" Killed " Output keyword meaning

While running a code in FreeFem++ I am getting an output : Killed . I will copy the last three lines of output from my output terminal .

SolverGMRES::dosolver1 1e-06 472592 4
fgmres: 0 residus 0 5.10454e+06 Cl: 5.10454e+06

Can someone please throw some lights on the matter . What does it mean and what are the probable cause and effect.