Spoil, botch, or bungle something, as in That was a great opportunity, but now I’ve blown it. [ ; c. 1940 ]
blow one’s lines. Make a mistake in speaking one’s part in a theatrical production, as in Ben blew his lines, but Dean came to the rescue. [ Mid-1900s ]
blow it out
blow it off
an act or instance of fellatio. See also oral sex. noun a slang term for fellatio noun Usage Note n.
a hinged mold for shaping molten glass during blowing.