a.

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

   那个婴孩在出牙齿，这几天一直烦躁不安。

2. 【医】过敏的
   Her skin is quite irritable.

   她的皮肤相当过敏。

3. 【生】易感受刺激的，应激性的

adj.

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