n. pl. d's or
D's also
ds or
Ds 1. The fourth letter of the modern English alphabet.
2. Any of the speech sounds represented by the letter d.
3. The fourth in a series.
4. Something shaped like the letter D.
5. D The lowest passing grade given to a student in a school or college.
6. Music a. The second tone in the scale of C major or the fourth tone in the relative minor scale.
b. A key or scale in which D is the tonic.
c. A written or printed note representing this tone.
d. A string, key, or pipe tuned to the pitch of this tone.