Real Dictionary

treat
countable noun: If you give someone a treat, you buy or arrange something special for them which they will enjoy.
singular noun: If you say that something is your treat, you mean that you are paying for it as a treat for someone else.
verb: If something is treated with a particular substance, the substance is put onto or into it in order to clean it, to protect it, or to give it special properties.
verb: If you treat someone or something in a particular way, you behave towards them or deal with them in that way.
verb: If you treat someone to something special which they will enjoy, you buy it or arrange it for them.
verb: When a doctor or nurse treats a patient or an illness, he or she tries to make the patient well again.

treat in American English
to deal with (a subject) in writing, speech, music, painting, etc., esp. in a specified manner or style
to discuss terms (with a person or for a settlement); negotiate
intransitive verb: to deal with a subject in speech or writing; discourse
noun: entertainment, food, drink, etc., given by way of compliment or as an expression of friendly regard
transitive verb: to act or behave toward (a person) in some specified way

treat in British English
noun: a celebration, entertainment, gift, or feast given for or to someone and paid for by another
verb: to deal with or regard in a certain manner