Source : Webster's Revised Unabridged Dictionary (1913)

Vap \Vap\ (v[a^]p), n. [See {Vapid}.]
   That which is vapid, insipid, or lifeless; especially, the
   lifeless part of liquor or wine. [Obs.]

         In vain it is to wash a goblet, if you mean to put into
         it nothing but the dead lees and vap of wine. --Jer.
                                                  Taylor.