alt.

/AE1 L T/
adjective
  1. 1

    Relating to a choice between two or more possibilities.

    โ€œan alternative propositionโ€

  2. 2

    Other; different from something else.

  3. 3

    Not traditional, outside the mainstream, underground.

  4. 4

    Alternate, reciprocal.

Source: https://en.wiktionary.org/wiki/alt., https://en.wiktionary.org/wiki/alternative