noun

1. the fourth letter of the Greek alphabet (Δ, δ)
2. something in the shape of a delta (Δ); specif., a tract of flat land, usually triangular, formed by deposits of soil and sand at the mouth of a large river

Etymology: L < Gr delta, of Sem orig., as in Heb dāleth, 4th letter of the alphabet, lit., door

adjective

1. of, in, or from the Delta Delta blues
2. Chem. see alpha