Cassmasculine (also called cassmasc) is a subset to cassgender where one feels that their gender is unimportant or where one is indifferent to the idea of gender, but knows that their gender is masculine in some way. Cassmasculine is different from a lack of gender, as a cassmasculine individual might have a gender but not feel that it's an important part of their identity, or they may not care about anything past the fact that their gender is more or less masculine.
The feminine counterpart is cassfeminine.
History
The term was coined by FANDOM user Rosalind Heks on June 9th of 2021.