plug_away
1. [ verb ] (work) work doggedly or persistently
Synonyms: slog keep_one's_nose_to_the_grindstone keep_one's_shoulder_to_the_wheel peg_away
Examples:

"She keeps plugging away at her dissertation"

Related terms: work plodder
2. [ verb ] persist in working hard
Synonyms: plug
Examples:

"Students must plug away at this problem"

Related terms: persevere