This is the 9156th most frequent Korean word.
거짓말이다
"거짓말이다" means "to be a lie" or "is a lie."
The word '거짓말이다' is used here to describe that the subject's statements are falsehoods.
그의 말은 모두 거짓말이다.
All his words are lies.
The word '거짓말이다' is used to express disbelief or describe an assertion as untrue emphatically.
이건 정말 거짓말이다, 믿을 수 없다!
This is truly a lie; I cannot believe it!
Here, '거짓말이다' is used hypothetically to consider the possibility that the assertion might be a falsehood.