When you share the same sex partner as someone you know, such as a friend or acquaintance. While sheath typically refers to a woman’s vagina, this term may be used by either men or women as long as the criterion is met.
Example 1
Man 1: “Hey, you fucked that girl over there?”
Man 2: “Yeah.”

Man 1: “Bro, me too! You’re my sheath buddy!”

Example 2
Girl: “I can’t believe he’s such a hoe. I must be sheath buddies with every bitch in this room!”
by SoliSlays April 8, 2020
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