labor, labour, toil, fag, travail, grind, drudge, dig, moil -- (work hard; "She was digging away at her math homework"; "Lexicographers drudge all day long")
churn, boil, moil, roil -- (be agitated; "the sea was churning in the storm")
moil -- (moisten or soil; "Her tears moiled the letter")
(TTS Sound)
