1. [from CB slang] An electronic pseudonym; a nom de guerre intended to conceal the user's true identity. Network and BBS handles function as the same sort of simultaneous concealment and display one finds on Citizen's Band radio, from which the term was adopted. Use of grandiose handles is characteristic of warez d00dz, crackers, weenies, spods, and other lower forms of network life; true hackers travel on their own reputations rather than invented legendry. Compare nick, screen name.
2. A magic cookie, often in the form of a numeric index into some array somewhere, through which you can manipulate an object like a file or window. The form file handle is especially common.
3. [Mac] A pointer to a pointer to dynamically-allocated memory; the extra level of indirection allows on-the-fly memory compaction (to cut down on fragmentation) or aging out of unused resources, with minimal impact on the (possibly multiple) parts of the larger program containing references to the allocated memory. Compare snap (to snap a handle would defeat its purpose); see also aliasing bug, dangling pointer.