Definition of "sound out"

sound out

verb
third-person singular simple present sounds out, present participle sounding out, simple past and past participle sounded out
1. (transitive) To question and listen attentively in order to discover a person's opinion, intent, or preference, especially by using indirect conversational remarks.
  Quotations
  You'll have to ask them—sound them out.
  1918, Peter B. Kyne, chapter 24, in The Valley of the Giants
2. (transitive) To pronounce a word or phrase by articulating each of its letters or syllables slowly in sequence.
3. (intransitive) To speak or sing loudly, to call out.
  Quotations
  Sound out, voices of young men! loudly and musically call me by my nighest name!
  c. 1855, Walt Whitman, Crossing Brooklyn Ferry, stanza 9