as·sid·u·ous \əˈsijəwəs, aˈ-\adjective Etymology: Latin assiduus, from assidēre to sit beside, take care of — more at assize 1.: marked or characterized by constant unremitting attention or by persistent energetic application < an assiduous servant > < assiduous labor > 2.: solicitous, obsequious Synonyms:see busy