Yes, signal is playable
...and is worth 10 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Signal" Definition
noun
A message communicated by such means.
An indicator, such as a gesture or colored light, that serves as a means of communication. See Synonyms at gesture.
Electronics An impulse or a fluctuating electric quantity, such as voltage, current, or electric field strength, whose variations represent coded information.
Something that incites action: The peace treaty was the signal for celebration.
The sound, image, or message transmitted or received in telegraphy, telephony, radio, television, or radar.
adjective
Notably out of the ordinary: a signal feat; a signal event.
Distinguished from the ordinary .
verb-intransitive
To make a signal or signals.
verb-transitive
To make a signal to: I signaled the driver to proceed.
To relate or make known by signals: They have signaled their willingness to negotiate.
verb
To communicate or indicate by or as if by .
To constitute a characteristic feature of (a meaningful linguistic form).
To make or send a signal.
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