ETYM Old Eng. busi, bisi, AS. bysig; akin to Dutch bezig, LG. besig; cf. Skr. bhűsh to be active, busy.
1. Crowded with or characterized by much activity.
2. Actively or fully engaged or occupied.
3. Overcrowded or cluttered with detail; SYN. fussy.
4. (Of facilities such as telephones or lavatories) Unavailable for use by anyone else or indicating unavailability; ('engaged' is a British term for a busy telephone line); SYN. engaged, in use.

To keep busy with; SYN. occupy.