The Collaborative International Dictionary of English v.0.48:

guidelines \guidelines\ n. hypen is changed from WN: adjust
   hier.
   a rule or set of rules giving guidance on how to behave in a
   situation.

   Note: a situation to which the guidelines are considered
         applicable is described as "falling within the
         guidelines"

   Syn: guideline, guidepost, rule of thumb.
        [WordNet 1.5]