Fetching details from the dictionary...
important condition; basic premise; basic assumption
something that should be obvious to all; something that should not have to be argued; something that goes without mentioning
major premise (in a syllogism)
安全が大前提のもとで計画を進める。
We proceed with the plan on the basic premise that safety comes first.
法律を守ることは社会生活の大前提だ。
Obeying the law is the basic premise of life in society.
この計画の大前提が崩れれば全体を見直す必要がある。
If the basic premise of this plan falls apart, the whole thing needs to be reconsidered.