a.

1. 草率从事的，轻率的
   Don't make a rash decision.

   别仓促作出决定。

2. 急躁的，鲁莽的
   It is rash to cross the street without looking both ways.

   不朝两边看看就穿马路是莽撞的。

n.

1. 疹，疹子[C]
   The girl broke out in a rash today.

   今天，这女孩身上出了疹子。

2. 一下子爆发的一连串（多指不愉快的事物）[S][（+of）]
   Students made a rash of complaints.

   学生们发出一片抱怨声。

adj.

n.

1. an area of redness and spots on the skin.
2. an unwelcome series of things happening within a short space of time:
   a rash of strikes.