swelled head

What you give a guy "upstairs" when complimenting him on the impressively "ballooned" status of his "crown" that he possesses "downstairs".

One should take care when verbally admiring a guy's desire-engorged "equipment" while you're also giving him a blowjob, since this may give him a major "swelled head" both "upstairs and down", and of course may also cause him to involuntarily make a huge mess all over your face in the process.