WordWeb Online

1. Preventing movement
   "the impeding crowds of revelers overflowing into the street";
   - clogging, hindering, obstructive

1. Be a hindrance or obstacle to
   "She is impeding the progress of our project";
   - hinder, fetter [literary], entrammel [literary], trammel [literary]
    
2. Block passage through
   "impede the path";
   - obstruct, obturate, occlude, jam, block, close up

See also: preventative, preventive

Type of: keep, prevent