MIT usage: (1) Exploring or visiting out-of-the-way places. Usually involves roofs, tunnels, or places behind locked doors around the MIT campus. Example usages include "I'm going hacking tonight" or "the hacking community". Related to the noun hack, involving a creative and non-destructive prank, but not the proper verb form of the noun.
(2) Working, usually involving programming. "I was hacking code all night."