Source : Webster's Revised Unabridged Dictionary (1913)

Sessile \Ses"sile\, a. [L. sessilis low, dwarf, from sedere,
   sessum, to sit: cf. F. sessile.]
   1. Attached without any sensible projecting support.

   2. (Bot.) Resting directly upon the main stem or branch,
      without a petiole or footstalk; as, a sessile leaf or
      blossom.

   3. (Zo["o]l.) Permanently attached; -- said of the gonophores
      of certain hydroids which never became detached.

Source : WordNet®

sessile
     adj 1: permanently attached to a substrate; not free to move about;
            "an attached oyster"; "sessile marine animals and
            plants" [syn: {attached}] [ant: {vagile}]
     2: attached directly by the base; not having an intervening
        stalk; "sessile flowers"; "the shell of a sessile barnacle
        is attached directly to a substrate" [syn: {stalkless}]
        [ant: {pedunculate}]