A brand of guitar effect pedals, owned by Roland. Their stuff is OK, but not nearly as "revolutionary" and "breakthrough" as they claim. They are rivaled by smaller companies that make far better stuff than theirs. Anything that has the Boss logo and the word "modeling" on the same device is gonna be crap. Their products are feature-limited, sometimes overpriced, and have been known to be unreliable. Boss can usually be summed up with one word: meh.
Inexperienced guitar player: "Dude, check it! I just got the new Boss ME-20! It is siiiickk. Goes right along with my Ibanez strat copy and tiny little 15W amp! Rock on Boss effects! METAL!!!"
Experienced guitar player: *facepalm*