Yes, solo is playable
...and is worth 5 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Solo" Definition
noun
A performance by a single singer or instrumentalist.
Games Any of various card games in which one player singly opposes others.
Music A composition or passage for an individual voice or instrument, with or without accompaniment.
Something undertaken or done alone .
Any of several card games in which a player elects to play without a partner against the other players.
adjective
Made or done by a single individual.
Music Composed, arranged for, or performed by a single voice or instrument.
Accommodating one person .
Of, relating to, or being a solo .
Hit with no runners on base .
verb-intransitive
To fly an airplane without a companion or an instructor, especially for the first time.
adverb
Unaccompanied; alone: flew solo from Anchorage to Miami.
verb
to perform by oneself as.
To perform a musical solo.
To fly an airplane without one's instructor on board .
To fly (as an airplane) alone.
To climb (as a mountain) alone.
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