Definify.com

Webster 1913 Edition

Adj.

Wrong in opinion or principle; having a perverse understanding; perverse.

–

Wrong′headˊed-ly

adv.

–

Wrong′headˊed-ness

Noun.

Macaulay.

, WRONGHEADED,

Adj.

[wrong and head.] Wrong in opinion or principle; having a perverse understanding; perverse.

See also: wrong-headed

wrongheaded ‎(comparative more wrongheaded, superlative most wrongheaded)

Having an obstinately (persistently, stubbornly) perverse/erroneous opinion or judgement.
He's not just wrong, but wrongheaded about raising the kids.