UNSOUND
unsound
(adjective) of e.g. advice
bad, unfit, unsound
(adjective) physically unsound or diseased; “has a bad back”; “a bad heart”; “bad teeth”; “an unsound limb”; “unsound teeth”
unsound
(adjective) not sound financially; “unsound banking practices”
unsound
(adjective) not in good condition; damaged or decayed; “an unsound foundation”
fallacious, unsound
(adjective) containing or based on a fallacy; “fallacious reasoning”; “an unsound argument”
Source: WordNet® 3.1
Etymology
Adjective
unsound (comparative more unsound or unsounder, superlative most unsound or unsoundest)
Not sound, particularly
Not whole, not solid, defective.
(especially of horses) Infirm, diseased.
(UK, especially of people) Not good, unreliable.
Antonyms
• sound
Source: Wiktionary
Un*sound", a.
Definition: Not sound; not whole; not solid; defective; infirm; diseased.
– Un*sound"ly, adv.
– Un*sound"ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition