godan verb (-su)
use thoroughly; use up; get the most out of
Implies using something until it is worn out, exhausted, or no longer useful; often carries a nuance of using something to its absolute limit.
新しいスマホを買ったら、前のを完全に使い倒すつもりだ。
Once I buy a new smartphone, I plan to use the old one until it's completely worn out.
He uses up almost his entire salary, pouring it into his hobby of photography.