godan verb (-ru)
sing energetically; sing with abandon
Describes singing with great energy, enthusiasm, or without restraint, often for an extended period. The auxiliary verb まくる adds the sense of doing something vigorously or non-stop.
See also: 捲る (まくる)
カラオケで一晩中歌いまくった。
I sang my heart out all night at karaoke.
彼女はステージで人
She energetically sang popular songs on stage.