What is "electrophilic substitution"

n. (context chemistry English) in aromatic organic chemistry, a form of substitution reaction in which the leaving functional group (normally hydrogen) is replaced with an electrophile

Electrophilic substitution reactions are chemical reactions in which an electrophile displaces a functional group in a compound, which is typically, but not always, a hydrogen atom. Electrophilic aromatic substitution reactions are characteristic of aromatic compounds, and are important ways of introducing functional groups onto benzene rings. The other main type of electrophilic substitution reaction is an electrophilic aliphatic substitution reaction.