signal

nouns

any nonverbal action or gesture that encodes a message
"signals from the boat suddenly stopped"
sign, signal, signaling
is derived from
signalize
is derived from
signalize
is derived from
signalize
is derived from
signalize
any incitement to action
"he awaited the signal to start"; "the victory was a signal for wild celebration"
signal
is a type of (narrower)
something that incites or provokes; a means of arousing or stirring to action
incitation, incitement, provocation
an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes
signal
is a type of (narrower)
energy made available by the flow of electric charge through a conductor
"they built a car that runs on electricity"
electrical energy, electricity

verbs

communicate silently and non-verbally by signals or signs
"He signed his disapproval with a dismissive hand gesture"; "The diner signaled the waiters to bring the menu"
sign, signal, signalise, signalize
is derived from
signaller
is derived from
signaler
is derived from
signaling
be a signal for or a symptom of
"These symptoms indicate a serious illness"; "Her behavior points to a severe neurosis"; "The economic indicators signal that the euro is undervalued"
bespeak, betoken, indicate, point, signal

adjectives

notably out of the ordinary
"the year saw one signal triumph for the Labour party"
signal
is similar to
making a strong or vivid impression
"an impressive ceremony"
impressive