a.

1. 易怒的，急躁的；煩躁的
   The baby is teething and has been irritable for several days.

   那個嬰孩在出牙齒，這幾天一直煩躁不安。

2. 【醫】過敏的
   Her skin is quite irritable.

   她的皮膚相當過敏。

3. 【生】易感受刺激的，應激性的

adj.

1. easily annoyed or angered.
2. Medicine  characterized by abnormal sensitivity.
3. Biology  able to respond actively to physical stimuli.