Indicates that a person(s)is making obvious boastful about themselves and/or their abilities. The term is said sarcastically, and "you" can be substituded with other pronouns.
You swear you're hot.
He swears that I like his ugly ass.
She swears she's all that in that leopard skin outfit.
you mean thats happening
"I just got some"
"You swear, got some"