The name “tomcat” refers to un-neutered male cats. This is mostly due to the difference in physical appearance from neutered male cats. They have several physical characteristics that separate them from neutered cats, including increased weight and muscle mass, a thicker neck and a bigger head.
The terms “shields” and “stud jowls” are used to describe the type of thicker face on a tom cat. However, by neutering a male cat before the age of 6 months, these characteristics do not develop. Neutering the male may also prevent aggressive behaviors, such as fighting, urine marking, wandering and other unwanted conduct.