1. [informal] Cease to live
   "The patient flatlined in the ER";
   - die, decease [archaic], perish, go, exit, pass away, expire, pass, kick the bucket [informal], cash in one's chips [informal], buy the farm [N. Amer, informal], conk [informal], give up the ghost [informal], drop dead [informal], pop off [informal], croak [informal], snuff it [informal], cash in [informal], cop it [Brit, informal], pop one's clogs [informal], pass on
    
2. Remain at a low level without increasing
   "the shares flatlined"

Derived forms: flatlining, flatlined, flatlines

Type of: change state, turn

Encyclopedia: Flatline