A gathering of people who sing to recorded music(noun)
Applied to music that people like to sing(adjective)
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Use "singalong" in a sentence
"The lovely production details that you lose on TV, the degree to which you lose yourself in a movie when the screen overwhelms you, make this a dandy "singalong" movie experience."
"Vladimir Putin consoles exposed Russian spies with 'singalong'"
"This was followed by a screened "singalong" and mini-dance class - both of which fell quite flat, with few youngsters in the audience willing to show themselves up by taking part."