out vs let on

out is a noun but let on is not a noun.

Word	Noun	Adjective	Verb	Adverb
out	Yes	Yes	Yes	Yes
let on	No	No	Yes	No

As verbs, let on is a hypernym of out; that is, let on is a word with a broader meaning than out:

out: reveal (something) about somebody's identity or lifestyle
let on: make known to the public information that was previously known only to a few people or that was meant to be kept a secret

Other hypernyms of out include break, bring out, disclose, discover, divulge, expose, give away, let out, reveal, uncover, unwrap.

As verbs, let on is a hypernym of out; that is, let on is a word with a broader meaning than out:

out: to state openly and publicly one's homosexuality
let on: make known to the public information that was previously known only to a few people or that was meant to be kept a secret

Other hypernyms of out include break, bring out, disclose, discover, divulge, expose, give away, let out, reveal, uncover, unwrap.

out (noun)	let on (noun)
(baseball) a failure by a batter or runner to reach a base safely in baseball

out (adjective)	let on (adjective)
not allowed to continue to bat or run
being out or having grown cold
outside or external
excluded from use or mention
not worth considering as a possibility
outer or outlying
directed outward or serving to direct something outward
knocked unconscious by a heavy blow
no longer fashionable
out of power; especially having been unsuccessful in an election

out (verb)	let on (verb)
be made known; be disclosed or revealed	make known to the public information that was previously known only to a few people or that was meant to be kept a secret
reveal (something) about somebody's identity or lifestyle
to state openly and publicly one's homosexuality

out (adverb)	let on (adverb)
away from home
from one's possession
moving or appearing to move away from a place, especially one that is enclosed or hidden