n.[C]

1. 信号；暗号[+to-v][+that]
   A red lamp is used as a danger signal.

   红灯用作危险信号。

2. 信号器；交通指示灯；【铁】信号机
   The train must stop when the signal's red.

   信号机是红色时，火车必须停驶。

3. 导因；近因；导火线[（+for）]
4. 标志；表示

a.

1. 作为信号的[B]
2. 显著的，非凡的
   This year has seen one signal triumph for them in the election.

   今年是他们在选举中取得重大胜利的一年。

vt.

1. 用信号发出；标志
   A period signals the end of a sentence.

   句号表示一个句子结束了。

2. 用信号通知，以动作向……示意[O2][+that]
   She signaled the car to stop by raising her hand.

   她举手示意车停下。

vi.

1. 发信号，打信号[（+to/for）]
   The teacher signaled for quiet.

   教师示意大家安静。

n.

1. a gesture, action, or sound conveying information or an instruction.
2. an indication of a state of affairs.
3. an event or statement that provides the impulse or occasion for something to happen.
4. a light or semaphore on a railway, giving indications to train drivers of whether or not to proceed.
5. Bridge  a prearranged convention of bidding or play intended to convey information to one's partner.
6. an electrical impulse or radio wave transmitted or received.

v.

1. transmit a signal.
2. instruct or indicate by means of a signal.

adj.