Definition of abstraction reaction

1) a reaction that takes any atom away from another chemical species. Classical examples in atmospheric chemistry are the gas phase removal of hydrogen from methane by hydroxyl radical or the following solution phase reaction: HSO3- + H2O2 ---> HSO4- +H2O

source: [Graedel, T.D. and Paul Crutzen. Atmospheric Change: an Earth system perspective; 1993; Freeman Press.]