ran·cor·ous \-k(ə)rəs\adjective : full of rancor : evincing or caused by rancor : deeply malevolent : malignant < preserve … from rancorous envy of the rich — Aldous Huxley > < a rancorous man, as petty and cruel as he was dictatorial — C.H.Grandgent > • ran·cor·ous·lyadverb