Verb (5-dan, つ, transitive)
1. to sever; to cut off
普通に考えれば、外への連絡を断つためだろう。If you think about it normally, it is probably to cut off contact with the outside.
2. to suppress; to eradicate; to exterminate
事故の原因を断つための対策が必要だ。We need measures to eliminate the causes of accidents.
3. to abstain (from); to give up
いちばん好きなものを断つ。You give up the thing you like most.