also: ウソくさい
i-adjective
suspicious; hard to believe; fishy
Describes a story, excuse, or claim that sounds made-up or unconvincing. Often used when something feels too convenient or unnatural to be true.
彼の言い訳はどうも嘘くさい。
His excuse sounds really fishy.
その話、嘘くさくて信じられないよ。
That story sounds so made-up, I can't believe it.
Compound of 嘘 (uso, 'lie') + くさい (kusai, suffix meaning 'smelling of' or 'reeking of'). The suffix くさい adds a negative, sensory judgment, giving the meaning 'stinks of a lie'.