Verb
lithen (third-person singular simple present lithens, present participle lithening, simple past and past participle lithened)
(archaic) To make lithe, soften; to ease, mitigate
lithen (third-person singular simple present lithens, present participle lithening, simple past and past participle lithened)
(dialectal) To thicken a broth or gravy with a thickening agent (e.g. flour, oatmeal, etc.)