List of diffident synonyms and diffident related words.
bashful, boggling, cautious, cowardly, coy, demure, demurring, deprecative, deprecatory, faltering, fearful, fearing, fearsome, goosy, hesitant, hesitating, in fear, jibbing, jumpy, modest, mousy, nervous, qualmish, rabbity, reluctant, retiring, scary, scrupling, scrupulous, self-deprecating, self-depreciating, self-depreciative, self-distrustful, self-doubting, self-effacing, shaky, shilly-shallying, shivery, shrinking, shy, skittery, skittish, squeamish, startlish, sticking, stickling, straining, tentative, timid, timorous, trembling, tremulous, trepidant, trigger-happy, unassertive, unassured, unselfconfident, unselfreliant