The Collaborative International Dictionary of English v.0.48:

Smother \Smoth"er\, v. t. [imp. & p. p. Smothered; p. pr. &
   vb. n. Smothering.] [OE. smotheren; akin to E. smoor. See
   Smoor.]
   1. To destroy the life of by suffocation; to deprive of the
      air necessary for life; to cover up closely so as to
      prevent breathing; to suffocate; as, to smother a child.
      [1913 Webster]

   2. To affect as by suffocation; to stife; to deprive of air
      by a thick covering, as of ashes, of smoke, or the like;
      as, to smother a fire.
      [1913 Webster]

   3. Hence, to repress the action of; to cover from public
      view; to suppress; to conceal; as, to smother one's
      displeasure.
      [1913 Webster]

WordNet (r) 3.0 (2006):

smothering
    adj 1: causing difficulty in breathing especially through lack
           of fresh air and presence of heat; "the choking June
           dust"; "the smothering soft voices"; "smothering heat";
           "the room was suffocating--hot and airless" [syn:
           smothering, suffocating, suffocative]