Keep your definition of mansex simple and open.  One simple definition of mansex is experiencing your inner and outer worlds, usually with your pants open.  Enjoying eroticism with another man can help you understand your own sexuality better.  Consider the following questions while forming your own definition of mansex:

Why do I masturbate?
Why do I want to share an orgasm with another man?
What do I feel when I ejaculate?
How do I position my body during solo or man-to-man action?
What do I think about as I approach shooting off?
How does my masculine sexuality help others?