Do you want to build a snowman
It's a way of secretly asking if you want to make out with the asker and eventually have sexual intercourse.
Example:
He: Hi there!
She: Hey, long time.
He: For sure. What are your plans for this weekend?
She: None. Do you want to build a snowman?
He: FINALLY!!
He: Hi there!
She: Hey, long time.
He: For sure. What are your plans for this weekend?
She: None. Do you want to build a snowman?
He: FINALLY!!