When you are in the act of coitus and a
guy or girl (because it could go both way) sticks their hand into the girls'
vagina for the pleasure of the girl. Similar to
fingering
1.
Sebastian "Dudeee, last night I was with this
fox and I stuck my hand in the cookie jar" ;)
2. Bianca "Hey girlyyyy, last night I was with this HOTTT
guy and he stuck his hand in the cookie jar!"