Meaning of INFORMAL in English
Informal speech or behaviour is relaxed and friendly rather than serious, very correct, or official.
She is refreshingly ~...
ADJ: usu v-link ADJ
She was always there at half past eight, chatting ~ly to the children.
ADV: ADV after v
He was overwhelmed by their friendly ~ity.
An ~ situation is one which is relaxed and friendly and not very serious or official.
The house has an ~ atmosphere.
Informal clothes are casual and suitable for wearing when you are relaxing, but not on formal occasions.
For lunch, dress is ~.
Everyone dressed ~ly in shorts or jeans.
You use ~ to describe something that is done unofficially or casually without planning.
The two leaders will retire to Camp David for ~ discussions.
ADJ: usu ADJ n
He began ~ly to handle Ted’s tax affairs for him.
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012