1.
to gradually become completely flat :
The hills first rose steeply then flattened out towards the sea.
2.
to stop growing or going up :
Export growth has started to flatten out.
1.
to gradually become completely flat :
The hills first rose steeply then flattened out towards the sea.
2.
to stop growing or going up :
Export growth has started to flatten out.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005