Noah Webster's Dictionary 1. (a.) Diligent; attentive; persistent; constant in application or attention; as, assiduous hard work; devoted; unremitting. 2. (a.) Performed with constant diligence or attention; unremitting; persistent; as, assiduous labor. Int. Standard Bible Encyclopedia ASSIDUOUS a-sid'-u-us: Occurs only in The Wisdom of Solomon 8:18 the Revised Version (British and American), "In assiduous communing with her is understanding," i.e. "in continued exercise of fellowship." The idea expressed in the adjective is contained in the prepositional prefix, sun of the original suggumnasia, giving the verb intensive force.