贿 is a bound form (b.f.) meaning 'bribe' — it almost always appears as part of two-character compounds like 贿赂 ('to bribe' or 'a bribe') and 行贿 ('to offer a bribe'). You won't use 贿 alone as a standalone word; it's a morpheme that combines with other characters to form the full verb or noun. The related word 受贿 means 'to accept a bribe'.