Source : Webster's Revised Unabridged Dictionary (1913)

Incremental \In`cre*men"tal\, a. (Biol.)
   Pertaining to, or resulting from, the process of growth; as,
   the incremental lines in the dentine of teeth.

Source : WordNet®

incremental
     adj : increasing gradually by regular degrees or additions;
           "lecturers enjoy...steady incremental growth in salary"