(grammar) A pronoun that does not specify the identity of its referent.

Without limit; forever, or until further notice; not definite. / Vague or unclear. / Undecided or uncertain. / (mathematics) Being an integral without specified limits.

(grammar) A word or phrase that designates an unspecified or unidentified person or thing or group of persons or things.

An indefinite pronoun used as a determiner.

Extremely persistent and untiring.

In an extremely persistent and untiring manner; in an indefatigable manner

In a manner that is not definite. / For a long time, with no defined end. / Forever.

Not defensible; not capable of being defended / Incapable of being justified or excused / Incapable of being explained

(military) A call sign which does not represent a specific facility, command, authority, activity, or unit, but which may represent any one or any group of these.

(mathematics) A function whose derivative is a given function; an antiderivative