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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)

subbed, subbing

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)

subbed, subbing

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.

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

The iTraxx Europe Sub Financials index of euro subordinated bonds CDS falls 3bps to 109bps.

From The Wall Street Journal • Mar. 19, 2026

The DJ traces this back to watching rave documentaries as a teenager and going to nights at Glasgow's legendary Sub Club venue.

From BBC • Apr. 25, 2025

A week after signing to Sub Pop with a handful of demos, he had to pause everything to react.

From Los Angeles Times • Apr. 21, 2025

Adebimpe, who is also an actor and appeared in the summer blockbuster “Twisters,” made a solo album due to come out in 2025 on Sub Pop.

From New York Times • Nov. 26, 2024

The eldest brother, Shin Tae Sub, was listed first.

From "Escape from Camp 14: One Man's Remarkable Odyssey from North Korea to Freedom in the West" by Blaine Harden