to be exhausted; to be tired out; to be worn out; to collapse (from exhaustion)
to be discouraged; to lose heart; to give in
マラソン後に完全にへたばっている。
I am completely exhausted after the marathon.
暑さでへたばりそうだったよ。
I almost collapsed from the heat.
マラソンの途中でへたばった選手が何人もいた。
Several runners collapsed from exhaustion partway through the marathon.