Soy boy

Soy boy is a pejorative term sometimes used in online communities to describe men perceived to be lacking masculine characteristics. The term bears many similarities and has been compared to the slang terms cuck (derived from cuckold), nu-male and low-T ("low testosterone")  terms sometimes used as insults for male femininity in the manosphere.

The term is based on the presence of the phytoestrogen isoflavone in soybeans, which has led some to claim that soy products feminize men who consume them, although there is a lack of evidence supporting the correlation between consumption of soy phytoestrogens and testosterone or estrogen levels or sperm quality.