The Collaborative International Dictionary of English v.0.48:

Exsert \Ex*sert"\, v. t. [imp. & p. p. Exserted; p. pr. & vb.
   n. Exserting.] [See Exsert, a., Exert.]
   To thrust out; to protrude; as, some worms are said to exsert
   the proboscis.
   [Webster 1913 Suppl.]