WordNet (r) 3.0 (2006):

rule out
    v 1: make impossible, especially beforehand [syn: preclude,
         rule out, close out]
    2: include or exclude by determining judicially or in agreement
       with rules [syn: rule out, rule in]
    3: dismiss from consideration or a contest; "John was ruled out
       as a possible suspect because he had a strong alibi"; "This
       possibility can be eliminated from our consideration" [syn:
       rule out, eliminate, winnow out, reject]