In physics, represents nuclear half life, or the wavelength of a ray/photon/light.
Used in the Half-Life games as the symbol for the rebellion. Also represents the game in general.
"Follow the lambdas spray-painted on the walls to a secret weapons cache."
"Ow, that Lambda made me bleed last night."
"That Lambda's thing was so big, I couldn't put my mouth around it."
Like the rainbow, the lambda is yet another cool symbol stolen by the gay community.
friend: HAHAHAHA!!! YOUR GAY! ROFL!!1
Everyone is doing it!