adj. 1 complete and unqualified; not superficial (needs a thorough change). 2 acting or done with great care and completeness (the report is most thorough). 3 absolute (a thorough nuisance). thorough bass a bass part for a keyboard player with numerals and symbols below to indicate the harmony. thorough-paced 1 (of a horse) trained to all paces. 2 complete or unqualified. thoroughly adv. thoroughness n.
[ orig. as adv. and prep. in the senses of through, f. OE thuruh var. of thurh THROUGH ]