To counterpoint is to contrast. If you point out that you should have class outside, someone might counterpoint by reminding you that it’s raining. In music, counterpoint is when two separate melodies are played or sung at the same time.
When a composer writes a piece of music using voices that follow different rhythms or pitches but ultimately come together harmonically, she uses counterpoint. You can also use this word as a verb to mean "to highlight difference:" "My tidy bookshelves counterpoint the mess of papers and books on my desk." The musical meaning of counterpoint, "pricking musical notes under the original melody on a manuscript," comes from an earlier sewing or quilting meaning.