chestnut Share definition Flag when a man ejaculates onto the breasts of a female sex partner When he knew he was about to cum he pointed his dick right at her huge tits. They both knew a chestnut was imminent. chestnut by Marchel March 20, 2013 Words you can keep railfan mug chonk mug chud mug based mug 67 mug slime mug mogging mug chopped mug thot mug glazing mug huzz mug yams mug larp mug unc mug cracked mug simp mug baddie mug bop mug lolcow mug