adj. 25B6; adjective
a tremulous voice : SHAKY, trembling, shaking, unsteady, quavering, wavering, quivering, quivery, quaking, weak; informal trembly, all of a tremble.
a tremulous smile : TIMID, diffident, shy, hesitant, uncertain, nervous, timorous, fearful, frightened, scared, anxious, apprehensive.
steady, confident.