plural signals
1
: an event or act which shows that something exists or that gives information about something : sign
The change in his behavior is clearly a signal [=indication] that there is a problem.
He likes her but he is sending the wrong signals with his constant teasing.
—often + ofInflammation is a signal of infection.
2
: something (such as a sound, a movement of part of the body, or an object) that gives information about something or that tells someone to do something
Don't start until I give the signal. [=sign]
The teacher gave us the signal to finish what we were working on and hand in our tests.
The pilot sent out a distress signal [=a message that the airplane was in danger] before the plane crashed.
They communicated with each other by using hand signals. [=movements of a person's hands that mean something]
3
: a piece of equipment with colored lights that is used on railways and roads to tell people when to go, to slow down, or to stop
Faulty wiring in the train station caused a signal to malfunction.
The traffic signal [=traffic light] was not working.
4
technical
a
: a message, sound, or image that is carried by waves of light or sound
The video/TV signal is scrambled.
Satellite dishes receive television signals.
a digital signal
The transmitter beams radio signals into space.
b
: a wave of light or sound that carries a message, sound, or image
We'll need better equipment to generate a 50 Hz signal.
signals; US signaled or British signalled; US signaling or British signalling
1
: to be a sign of (something) : to show the existence of (something)
Robins signal the arrival of spring.
The election results surely signal the start/beginning of a new era.
He signaled [=showed, communicated] his irritation by sighing and rolling his eyes dramatically.
Redness, swelling, and painful itching signal [=indicate] an infection.
A lock on the suitcase might signal that there's something of value inside.
2
: to make a sound or motion that tells someone something
Did he signal before he made the left turn?
They signaled at me to come over to their table.
We signaled for help.
He signaled us that it was time to begin the meeting.
The umpire signaled a strike.
always used before a noun
formal
: very important or great : significant
Is he worthy of such a signal honor?
The bill's passage was a signal [=notable] victory for environmentalists.
Cite this Entry
“Signal.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/signal. Accessed 22 Jun. 2026.
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