Vulgar slang term for tribadism, the lesbian act of rubbing or grinding vulva-to-vulva for sexual stimulation. "Clam transfer" entered the national lexicon thanks to a wonderful Progresso Soup commercial first airing in 2010.
Sometimes when two lesbians love each other very much, they will engage in a clam transfer to physically express that love.
by The Other Guido February 26, 2010