Wordnet 3.0
VERB (1)
1. 
 become less in amount or intensity; 
- Example: "The storm abated"- Example: "The rain let up after a few hours"[syn: abate, let up, slack off, slack, die away]
WordNet (r) 3.0 (2006):
slack off
    v 1: become less in amount or intensity; "The storm abated";
         "The rain let up after a few hours" [syn: abate, let
         up, slack off, slack, die away]