WordWeb Online

1. Leave furtively and stealthily
   - steal away, sneak away, sneak off, sneak out, slip 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, slipping away, slipped away

See also: glide, steal

Type of: advance, go away, go forth, go on, leave, march on, move on, off [informal], pass on, progress