I. ˈ ̷ ̷ˌ ̷ ̷ noun
Etymology: let down
1.
a. : a source or mood of mental depression : discouragement , disappointment
the enterprise … has been a big letdown to those of us who had high hopes for it — E.R.Bentley
the balance of the collection is a sad letdown — J.F.McComas
came home … with a vague feeling of letdown about Italian art — R.M.Coates
b. : a slackening of effort : relaxation , defection
the sudden letdown from discipline — Dixon Wecter
at that time of day, a general air of letdown hung over the kitchen — Joseph Wechsberg
specifically : a lapse from high moral standards
how hard as stone people are about other folks' letdowns — Dorothy C. Fisher
2. : a drop in amount or volume : decline , slump
an amazing buying rush was resumed after a brief letdown — New York Times
the letdown in steel production … brought moderate declines in sales — Newsweek
a normal seasonal decline is expected but no general business letdown is in sight
3. : the descent of an airplane from cruising altitude to the point at which a landing approach is begun
cross-country flying and instrument letdowns at strange airfields — Crowsnest
4. usually let-down “ : a physiological response of a lactating mammal to suckling or allied stimuli whereby increased intramammary pressure forces previously secreted milk from the acini and finer tubules into the main collecting ducts whence it can be drawn through the nipple
II. adjective
1. : characterized by mental lassitude : depressed , dispirited
the letdown feeling that comes with emptying ashtrays after a party
2. : of or relating to the gradual descent of an airplane
letdown procedure
the first letdown point after Honolulu — Sperryscope