1
beginning and end
前の会社では何でも屋に終始したので今度は専門職に就きたい。
I wore several hats at my last office so I'd like to specialize this time.
2
doing something from beginning to end;being unchanged from beginning to end
私服警官が終始大統領の身辺を固めていた。
The private detectives accompanied the President everywhere.
3
from beginning to end;the whole time;throughout;consistently