WordWeb Online

1. Leave furtively and stealthily
   - steal away, sneak away, sneak off, sneak out
    
2. Become later by the passage of a given amount of time
   "three years slipped away"
   - elapse, lapse, pass, slip by, glide by, go by, slide by, go along

Derived forms: slips away, slipped away, slipping away

See also: slip

Type of: advance, go away, go forth, go on, leave, march on, move on, pass on, progress