let down

verb

1. (also preposition) to lower

2. to fail to fulfil the expectations of (a person); disappoint

3. to undo, shorten, and resew (the hem) so as to lengthen (a dress, skirt, etc)

4. to untie (long hair that is bound up) and allow to fall loose

5. to deflate

   to let down a tyre

noun

1. a disappointment

2. the gliding descent of an aircraft in preparation for landing

3. the release of milk from the mammary glands following stimulation by the hormone oxytocin

Idioms and Phrases

Cause to descend, lower, as in They let down the sails . [Mid-1100s]

Also, let up . Slacken, abate, as in Sales are letting down in this quarter , or They didn't let up in their efforts until the end . The first term dates from the mid-1800s, the variant from the late 1700s.

See let someone down . Also see let one's hair down .