"The Collaborative International Dictionary of English v.0.48"
Assiduous As*sid"u*ous, a. L. assiduus, fr. assid?re to sit
near or close; ad + sed=ere to sit. See Sit.
1. Constant in application or attention; devoted; attentive;
unremitting.
1913 Webster

She grows more assiduous in her attendance.
--Addison.
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2. Performed with constant diligence or attention;
unremitting; persistent; as, assiduous labor.
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To weary him with my assiduous cries. --Milton.
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Syn: Diligent; attentive; sedulous; unwearied; unintermitted;
persevering; laborious; indefatigable.
1913 Webster As*sid"u*ous*ly, adv. --
As*sid"u*ous*ness, n.
1913 Webster