The Collaborative International Dictionary of English v.0.48:

Causal \Caus"al\, a. [L. causalis. See Cause.]
   Relating to a cause or causes; inplying or containing a cause
   or causes; expressing a cause; causative.
   [1913 Webster]

         Causal propositions are where two propositions are
         joined by causal words.                  --Watts.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Causal \Caus"al\, n.
   A causal word or form of speech.
   [1913 Webster]

         Anglo-Saxon drencan to drench, causal of Anglo-Saxon
         drincan to drink.                        --Skeat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

causal
    adj 1: involving or constituting a cause; causing; "a causal
           relationship between scarcity and higher prices"