the young of certain large predatory animals such as bears, lions, wolves, and other big cats; analogous to a canine pup (also in some of the following meanings)
by analogy a human youth, especially one who is inexperienced, awkward, or ill-mannered, boy or (rarer, in some senses only fairly recent) girl, especially:
a younger, thinner, less hairy and/or smaller member of the Bear subculture. Typically assumed to be less experienced in the Bear subculture, and/or to be bottoms.