all possible means; every measure
Often used in phrases like 万策尽きる (to exhaust all options) or 万策を講じる (to take every possible measure). Conveys a sense of exhaustive effort or complete set of strategies.
Having exhausted all possible means, he finally gave up.
The government took every possible measure to prevent the spread of infection.
Compound of 万 (ban, 'ten thousand; all') and 策 (saku, 'plan; measure'). The combination straightforwardly means 'all possible plans or measures'.