Keeping a lot of state in your head while modifying a program. "Don' t bother me now, I' m juggling eggs", means that an interrupt is likely to result in the program' s being scrambled. In the classic first-contact SF novel "The Mote in God' s Eye", by Larry Niven and Jerry Pournelle, an alien describes a very difficult task by saying "We juggle priceless eggs in variable gravity." See also hack mode. [Jargon File]