Answer:
Yes; That's what gay means, you want (or have) sexual relations with someone from your own sex. You can be bisexual, but the act of male-male sex is a homosexual act. Being on the "down low" doesn't make it "just messing around" male on male is a homosexual act.
Note: some people experiment with sexual behavior with the same sex, this doesn't make them specifically gay (the act is) - your orientation is based on whom you choose to love romantically. There are some people who are gay who never have gay sex. Being gay isn't about sex, it's about love.