Similar to "cuck", Soy Boy is a pejorative term used by the alt-right to describe men on the left. It is based off the high contents of phytoestrogen — a plant-based chemical that potentially has estrogenic effects when eaten. Estrogen is a hormone involved in female body development, but is also naturally found at lower levels in men. Alt-right men such as Paul Joseph Watson have claimed that consuming soy will make men "girly", even though no science has pointed to high consumption of soy "feminizing" men. The alt-right uses this as "proof" that the person they're talking about is a girly-man to mock and brush off. See beta.