To insert one's middle, ring and index finger into a vagina and with your thumb against her clitoris and your little finger on her perinium (better known as the taint). You rotates your wrist to stimulate the clit/perinium and move inside her.
I gave my girlfriend a gentleman's handshake last night.
A gentleman's handshake is when one man inserts his hand into a woman's vagina and another man inserts his hand into the same woman's anus and the two men's hands meet somewhere inside her and they give a handshake.
Timmy walked into his mother's bedroom without knocking and saw that his father and uncle where engaged in a gentleman's handshake to the pleasure of his mother.