A term used by many, generally in reference to someone who may be trying to make something or someone look appealing or attractive when it quite clearly will not work, or will only deceive the dumbest of people.
Car salesmen are generally good at "putting lipstick on a pig" because they are always selling unroadworthy buckets of shit and try and hide their shitfulness by tarting them up.
The dude in that car yard just put a body kit on that piece of shit. Talk about putting lipstick on a pig
