verb. Present participle of heighten.

adjective. reaching a higher intensity

"He borrows only to shew his own Talents in heightening, refining and polishing all that is furnished him by others, and thereby secures his Character as a fine Writer, from being confounded with that of the Dull Copyer."

intensifying  

brightening  enlightening  frightening  lightening  lightning  

accelerando  acceleration  aggrandizement  aggravation  amplification  

heighten