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• sub
  sub

  noun

  a submarine.
• SUB
  SUB

  abbreviation

  supplemental unemployment benefits.
• sub-
  sub-

  a prefix occurring originally in loanwords from Latin (subject; subtract; subvert; subsidy ); on this model, freely attached to elements of any origin and used with the meaning “under,” “below,” “beneath” (subalpine; substratum ), “slightly,” “imperfectly,” “nearly” (subcolumnar; subtropical ), “secondary,” “subordinate” (subcommittee; subplot ).
• sub.
  sub.

  abbreviation

  subordinated.
• sub–
  sub–

  A prefix that means “underneath or lower” (as in subsoil), “a subordinate or secondary part of something else” (as in subphylum.), or “less than completely” (as in subtropical.)

sub

¹ American  

[suhb] / sʌb /

noun

1. a submarine.

2. a substitute.

   We've got a sub in English this week because our teacher's home with the flu.

3. a submarine sandwich.

4. a submissive in a BDSM sexual encounter or relationship.

5. a subcontractor.

6. a sublieutenant.

7. a subordinate.

8. a subaltern.

9. British. an advance against one's wages, especially one granted as a subsistence allowance.

10. Photography. a substratum.

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verb (used without object)

subs, present (3rd person singular) subbed, past participle, past subbing present participle

1. to act as a substitute for another.

2. to act as the submissive partner in a BDSM sexual encounter or relationship.

verb (used with object)

subs, present (3rd person singular) subbed, past participle, past subbing present participle

1. Photography. to coat (a film or plate) with a substratum.

SUB ² American  

abbreviation

1. supplemental unemployment benefits.

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sub- ³ American  

1. a prefix occurring originally in loanwords from Latin (subject; subtract; subvert; subsidy ); on this model, freely attached to elements of any origin and used with the meaning “under,” “below,” “beneath” (subalpine; substratum ), “slightly,” “imperfectly,” “nearly” (subcolumnar; subtropical ), “secondary,” “subordinate” (subcommittee; subplot ).

2. Chemistry.

   1. a prefix indicating a basic compound.

      subacetate; subcarbonate; subnitrate.

   2. a prefix indicating that the element is present in a relatively small proportion, i.e., in a low oxidation state.

      subchloride; suboxide.

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sub. ⁴ American  

abbreviation

1. subordinated.

2. subscription.

3. substitute.

4. suburb.

5. suburban.

6. subway.

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sub- ¹ British  

prefix

1. situated under or beneath

   subterranean

2. secondary in rank; subordinate

   subeditor

3. falling short of; less than or imperfectly

   subarctic

   subhuman

4. forming a subdivision or subordinate part of a whole

   subcommittee

5. 1. indicating that a compound contains a relatively small proportion of a specified element

      suboxide

   2. indicating that a salt is basic salt

      subacetate

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sub ² British  

/ sʌb /

noun

1. short for several words beginning with sub- See subaltern subeditor submarine subordinate subscription substandard substitute substratum

2. Formal term: subsistence allowance.  informal an advance payment of wages or salary

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verb

1. (intr) to serve as a substitute

2. informal (intr) to act as a substitute (for)

3. informal to grant or receive (an advance payment of wages or salary)

4. informal (tr) short for subedit

5. (tr) photog to apply a substratum to (a film or plate base)

sub. ³ British  

abbreviation

1. subeditor

2. subito (in music)

3. subscription

4. substitute

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sub– Scientific  

1. A prefix that means “underneath or lower” (as in subsoil), “a subordinate or secondary part of something else” (as in subphylum.), or “less than completely” (as in subtropical.)

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Regionalisms

See hero sandwich.

Other Word Forms

Conjugated Forms

Present

• has subbed
  perfect 3rd person singular
• have subbed
  perfect
• have been subbing
  perfect progressive
• are subbing
  progressive
• is subbing
  progressive 3rd person singular
• am subbing
  progressive 1st person singular
• has been subbing
  perfect progressive 3rd person singular
• subs
  singular 3rd person
• subbing
  participle

Past

• had subbed
  perfect
• were subbing
  progressive plural
• subbed
  simple
• subbed
  participle
• was subbing
  progressive singular
• had been subbing
  perfect progressive

Future

• will sub
  simple
• will have subbed
  perfect
• will be subbing
  progressive
• will have been subbing
  perfect progressive

Etymology

Origin of sub¹

By shortening of words prefixed with sub-

Origin of sub-³

< Latin, combining form representing sub (preposition); akin to Greek hypó; see hypo-

Explanation

If a history buff mentions a sub, she's probably referring to an underwater warship. But if your friend wants a sub for lunch, he hasn't suddenly developed a taste for warships — he just wants a sandwich. Sub is short for submarine, the cylindrical watercraft with rounded ends that can operate deep beneath the water. Sub can also refer to a long sandwich filled with meat, cheese, and veggies; this kind of sub goes by different names in different parts of the country, including hero, hoagie, and grinder. The sub in your geometry classroom is probably just a substitute teacher.

Example Sentences

Watch out for him as a super sub.

From BBC • Jun. 9, 2026

"He's tiny! It's blue!" one excited scientist was recorded as saying when she first caught sight of the cerulean cephalopod on footage transmitted from the sub.

From Barron's • May 25, 2026

Here, she does have five goals as a sub since June 2022, including her heroics in knockout rounds.

From BBC • Apr. 25, 2026

To avoid paying twice—once to the sub and again to the contractor—get a release of claims and a lien waiver from the sub.

From The Wall Street Journal • Apr. 25, 2026

The Hunley was the first submarine to sink an enemy ship, but it was not the first sub to be used in wartime, nor was it the first to attack an enemy vessel.

From "Shipwrecked!" by Martin W. Sandler