鞭 (biān) is a noun that primarily means 'whip'. It can also refer to a string of firecrackers, especially in the phrase 一挂鞭. Historically, it denoted an iron staff used as a weapon. As a verb, 鞭 means 'to flog' or 'to lash', but this entry covers only noun uses. The slang sense for penis is vulgar and not used in polite conversation.