Definition of "misadventure"

It is said that every life has its roses and thorns; there seemed, however, to have been a misadventure or mistake in Stephen's case, whereby somebody else had become possessed of his roses, and he had become possessed of the same somebody else's thorns in addition to his own.

1854, Charles Dickens, “Stephen Blackpool”, in Hard Times. For These Times, London: Bradbury & Evans, […], book the first (Sowing), page 75

There were, however, 34 deaths among passengers in movement accidents, due mainly to misadventure and carelessness when entering and leaving trains in motion, falling off platforms and out of carriages, and opening and closing carriage doors.

1960 December, “Talking of Trains: B.R. safety in 1959”, in Trains Illustrated, page 708