a.

1. 立即的，即刻的
   The telegram asked for an instant reply.

   这封电报要求立即回复。

2. 紧迫的，迫切的；迫在眉睫的
   The flood victims were in instant need of help.

   水灾难民急需救助。

3. （食品）速食的；速溶的
   He often eats out at an instant Chinese restaurant.

   他常在一家中式快餐馆吃饭。

4. 本月的

n.

1. 顷刻，一刹那[S1]
   An instant later the explosion occurred.

   一会儿之后，爆炸就发生了。

adj.

1. happening immediately.
   ▸(of food) processed to allow quick preparation.
2. dated urgent; pressing.
3. [postpos.] dated (in business letters) of the current month:
   your letter of the 6th instant.
4. archaic of the present.

n.

1. a precise moment of time.
2. a very short time.