I.R.

1. immediate reserve.

2. infantry reserve.

3. intelligence ratio.

4. internal revenue.

* * *

ir-¹,

prefix. the form of in-¹ (Cf. ↑in-) (not) before r, as in irrational, irregular, irresistible.

ir-²,

prefix. the form of in-² (Cf. ↑in-) (in) before r, as in irrigate.

Ir (no period),

iridium (chemical element).

Ir.,

1. Ireland.

2. Irish.

IR (no periods),

1. information retrieval.

2. infrared.

I.R.,

1. British. Inland Revenue.

2. Internal Revenue.