of the voice Quivering as from weakness or fear:
— Spoke timidly in a tremulous voice.

synonym: quavering.

Roget 860: fearing etc. v.; frightened etc. v.; in fear, in a fright etc. n.; haunted with the fear of etc. n.; afeard^†.    afraid, fearful; timid, timorous; nervous, diffident, coy, faint-hearted, tremulous, shaky, afraid of one's shadow, apprehensive, restless, fidgety; more frightened than hurt.    aghast; awe-stricken, horror-stricken, terror-stricken, panic-stricken, awestruck, awe-stricken, horror-struck; frightened to death, white as a sheet; pale, pale as a ghost, pale as death, pale as ashes; breathless, in hysterics.    inspiring fear etc. v.; alarming; formidable, redoubtable; perilous etc. (danger) 665; portentous; fearful; dread, dreadful; fell; dire, direful; shocking; terrible, terrific; tremendous; horrid, horrible, horrific; ghastly; awful, awe-inspiring; revolting etc. (painful) 830; Gorgonian.    ... show more

Roget 605: irresolute, infirm of purpose, double-minded, half-hearted; undecided, unresolved, undetermined; shilly-shally; fidgety, tremulous; hesitating etc. v.; off one's balance; at a loss etc. (uncertain) 475.    vacillating etc. v.; unsteady etc. (changeable) 149; unsteadfast^†, fickle, without ballast; capricious etc. 608; volatile, frothy; light, lightsome, light-minded; giddy; fast and loose.    weak, feeble-minded, frail; timid, wimpish, wimpy etc. 860; cowardly etc. 862; dough-faced [U.S.]; facile; pliant etc. (soft) 324; unable to say 'no', easy-going revocable, reversible.    ... show more

Roget 583: stammering etc. v.; inarticulate, guttural, nasal; tremulous; affected.