A nonaggression pact is an agreement between two or more governments to abstain from waging war on each other. Nonaggression pacts may lead to mutual cooperation in some matters and expanded trade, however they are not as strong as formal alliances.
The Dominion signed nonaggression pacts with the Tholians, the Miradorn, the Romulan Star Empire and Bajor prior to the beginning of the Dominion War. The Romulans withdrew from their agreement after Senator Vreenak, the man who negotiated the Romulan pact, was apparently assassinated by the Dominion. (DS9: "Call to Arms", "In the Pale Moonlight")
In 2376, Kathryn Janeway negotiated a nonaggression pact with the Terkellians. (VOY: "The Voyager Conspiracy")