Synonyms for Whisper:

n.

put out, aside, confidence, secret, let it be known that, proclaim, disseminate, announce, hint, disclose, broadcast, reveal, rumor, disclosure, spread. gurgle, fizz, growl, sigh, babble, putter, cluck, grunt, sough. dash, suspicion, breath, touch, pitter-patter, hair, ripple, peep, taste, shade, tinge, shadow, streak, ghost, semblance, pit-a-pat, whisker, whiff, intimation, pad, big, show, trace, suggestion. croon, under your breath, bleat, purr, croak, breathe. ramble, stage whisper, burble, patter, ramblings, jabber, meander. communication (noun)
whispering, susurration.
quietness (noun)
mumble, softness, undertone, faintness, lowness.
rumor; information expressed in soft voice (noun)
report, mumble, hum, disclosure, buzz, mutter, confidence, susurration, word, sigh, secret, murmur, hint, undertone.
sibilation (noun)
sibilation, rhonchus.
susurration (noun)
susurration.
trace, suggestion (noun)
suspicion, breath, dash, tinge, touch, whiff, shadow, shade.
voice (noun)
intonation, articulation, emission, pronunciation, speech, utterance, exclamation, enunciation.
whisper (noun)
susurration, rustling, rustle, whispering.

v.

sibilate (verb)
snuffle, sputter, sizzle, sneeze, lisp, zip, buzz, wheeze, hiss, whistle, sniffle, whoosh, snort, whiz, snore, whir, fizzle, sibilate.
speak softly (verb)
hiss, sibilate, breathe.
voice (verb)
murmur, groan, exclaim, emit, articulate, moan, cry, speak, voice, pronounce, mutter, intone, enunciate, utter.

Other synonyms:

sigh, stage whisper, ramblings, croon, hint. whiff, whisker, purr. intimation, ramble, semblance, bleat, croak. patter, tinge, burble, streak, hair, ghost. shadow. trace, breath. breathe. shade. blow
whiff.
bubble
fizz.
buzz
hum.
moan
sough.

Usage examples for whisper

  1. It is I." " There," said Marie, in a whisper – The Last Hope by Henry Seton Merriman
  2. " Is it-" began the lady, in an agitated whisper – Cy Whittaker's Place by Joseph C. Lincoln
  3. Guy Little's voice was now a whisper – Man to Man by Jackson Gregory