breve: In music, the breve has the longest value of any note. It's twice as long as a whole note. Because it's so long, you don't see it very often. It won't fit into most single measures, but occasionally a piece is written in a 4/2 time signature (each measure is four half notes long), and a breve fills the entire measure.
The other note values -- the quarter note, eighth note, and so on -- think the breve is a selfish, gluttonous dick. The breve is so fat, in fact, that it takes four note stems to keep it from spilling out an completely obliterating the measure!