The word "singin" is a shorter form of the word "singing." It refers to the act of producing musical sounds with the voice, usually in a melodious way. Full definition
And Americans may continue to Hope that Gabriel Likes their Music, and I would add, to hope that they can join Billy Graham and Martin Luther King, Jr. in singin» «Amazing Grace» as they parade down the Azusa St. of the hereafter. (firstthings.com)
With the city still recovering from the devastating effects of Hurricane Harvey, it was fitting that HCAF 2017 featured a screening of Singin» in the Rain. (nerdlocker.com)
But the show is stolen by a heavily trailed set piece between Hobie and Mr Laurentz («Would that it were so simple»), which splendidly reworks the elocution riffs of Jean Hagen and Kathleen Freeman's «I can't stand him» routine from Singin» in the Rain; the fact that the joke is still funny second time round is a testament to its roadworthiness. (theguardian.com)