know by heart (verb) know by heart: have absolute knowledge
Sinonime: afraid, averse, backward, dawdling, delaying, diffident, disinclined, doubtful, doubting, faltering, half-hearted, halting, hanging back, hesitating, indecisive, irresolute, lacking confidence, lazy, loath, pendulous, reluctant, shilly-shally, shy*, skeptical, slow, tentative, timid, uneager, unpredictable, unsure, unwilling, vacillant, vacillating, wavering