[countable, usually singular, uncountable] decline (in something) | decline (of something) a continuous decrease in the number, value, quality, etc. of something a rapid/sharp/gradual decline urban/economic decline The company reported a small decline in its profits. An increase in cars has resulted in the decline of public transport. The town fell into (a) decline(= started to be less busy, important, etc.) after the mine closed. Industry in Britain has been in decline since the 1970s.