거짓말하다 (keojinmalhada) means “lie”

More examples

동생이 거짓말해서 혼났어요.tong saeng i keo jin mal hae seo hon na sseo yo

My younger sibling was scolded for lying.

False words are spoken as though they were facts.

속이다sogida: Make someone believe something untrue by hiding or changing the truth.
뻥치다ppeongchida: Tell a lie in a very casual, informal way.

진실이 아닌 말을 사실처럼 다른 사람에게 말하다chin si ri a nin ma reul sa sil cheo reom ta reun sa ra me ge mal ha da

The verb 거짓말하다 (geojinmalhada, "to lie") comes from 거짓 (geojin, "falsehood") and 말 (mal, "words") plus 하다 (hada, "to do").

English uses one short verb, but Korean often builds this action with a noun and a general action verb, a pattern that appears in many everyday expressions.