What does "buckle down" mean?

To apply oneself to study, or a task or work; to focus on or take a serious attitude towards something; to put forth the needed effort.

What is a synonym for "buckle down"?

Common synonyms include: address, apply, attack, be determined, be in earnest, be resolved.

verb

verb ·Rare ·Advanced level

Verb

1
To apply oneself to study, or a task or work; to focus on or take a serious attitude towards something; to put forth the needed effort. idiomatic, intransitive
"If he would buckle down and do his homework, he could be an excellent student."
2
work very hard, like a slave wordnet

"If he would buckle down and do his homework, he could be an excellent student."

From buckle + down.