flat ‧ line /ˈflætlaɪn/ BrE AmE verb
be flatlining to be at a low level or standard that is neither increasing nor decreasing:
The Tories have been flatlining in the polls.
flat ‧ line /ˈflætlaɪn/ BrE AmE verb
be flatlining to be at a low level or standard that is neither increasing nor decreasing:
The Tories have been flatlining in the polls.
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012