A debilitating disease where your breasts shrink and eventually fall off.
I lost my breasts to the beibhinn.
by ghale June 5, 2021
Someone who you think is your friend but then totally backstabs you and leaves you alone.
“Wow she just like totally stole your boyfriend from you.”

“Omg it must be a beibhinn.”
by Sofieeeeeeeee November 2, 2019