Definitions for "Indefinite article"
the determiners "a" and "an".
a determiner (as `a' or `some' in English) that indicates non-specificity of reference
The words a and an in English. Indefinite articles are used to introduce a noun as a member of a class of nouns, or to make generalizations about a whole class or group of nouns e.g. Please hand me pencil. An ocean is large body of water.