n. （河流的）三角洲 （delta的复数形式）

Delta \Del"ta\, n.; pl. {Deltas}. [Gr. de`lta, the name of the
fourth letter of the Greek alphabet (the capital form of
which is [Delta], Eng. D), from the Ph[oe]nician name of the
corresponding letter. The Greeks called the alluvial deposit
at the mouth of the Nile, from its shape, the Delta of the
Nile.]
1. The fourth letter of the Greek alphabet ([Delta] [delta]),
corresponding to {D}. Hence, an object having the shape of
the capital [Delta].
[Webster 1913 Suppl.]

2. A tract of land shaped like the letter delta ([Delta]),
especially when the land is alluvial and inclosed between
two or more mouths of a river; as, the delta of the
Ganges, of the Nile, or of the Mississippi.

3. (Elec.) The closed figure produced by connecting three
coils or circuits successively, end for end, esp. in a
three-phase system; -- often used attributively, as delta
winding, delta connection (which see), etc.
[Webster 1913 Suppl.]