Denki Anma (literally "electric massage") is a technique originating in pro wrestling, whereby the user grabs the victim by his feet and uses the leverage to grind his own foot into the victim's crotch. It has since become a technique adapted for use in S&M play.

Note: The pixiv tag "電マ":http://dic.pixiv.net/a/%E9%9B%BB%E3%83%9E is not an abbreviation for 電気アンマ. It is a common name for [[Hitachi Magic Wand]].
電気按摩 電気あんま 電気アンマ