The Collaborative International Dictionary of English v.0.48:

Milksop \Milk"sop`\, n.
   A piece of bread sopped in milk; figuratively, an effeminate
   or weak-minded person. --Shak.
   [1913 Webster]

         To wed a milksop or a coward ape.        --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

milksop
    n 1: a timid man or boy considered childish or unassertive [syn:
         sissy, pantywaist, pansy, milksop, Milquetoast]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "milksop":
   Lord Fauntleroy, Milquetoast, Percy, ass, baby, big baby,
   born fool, buffoon, caitiff, chicken, chicken liver, clown, coward,
   cream puff, crybaby, dastard, doodle, doormat, dull tool,
   effeminate, egregious ass, figure of fun, fool, fraid-cat,
   fraidy-cat, funk, funker, goody-goody, gutless wonder, ignoramus,
   invertebrate, jackass, jellyfish, lightweight, lily, lily liver,
   lunatic, meek soul, mollycoddle, mooncalf, mouse, namby-pamby,
   nance, nancy, nebbish, nonentity, old woman, pansy, pantywaist,
   perfect fool, poltroon, pushover, sad sack, scaredy-cat, schmuck,
   sissy, softhead, softling, softy, sop, stupid ass, tomfool,
   weak sister, weakling, white feather, white liver, zany