The Collaborative International Dictionary
Hoarsening
Hoarsen \Hoars"en\, v. t. [imp. & p. p. Hoarsened; p. pr. & vb. n. Hoarsening.] To make hoarse.
I shall be obliged to hoarsen my voice.
--Richardson.
Wiktionary
hoarsening
vb. (present participle of hoarsen English)