The Collaborative International Dictionary of English v.0.48:

Subsumption \Sub*sump"tion\, n.
   1. The act of subsuming, or of including under another.
      [1913 Webster]

            The first act of consciousness was a subsumption of
            that of which we were conscious under this notion.
                                                  --Sir W.
                                                  Hamilton.
      [1913 Webster]

   2. That which is subsumed, as the minor clause or premise of
      a syllogism.
      [1913 Webster]

            But whether you see cause to go against the rule, or
            the subsumption under the rule.       --De Quincey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

subsumption
    n 1: the premise of a syllogism that contains the minor term
         (which is the subject of the conclusion) [syn: minor
         premise, minor premiss, subsumption]
    2: incorporating something under a more general category