An intercept course, also known as an interception course or intercept vector, was a navigational path by which one vessel journeyed toward another, typically with the intent of engaging the target in combat. It was a concept known to several space faring cultures. Often, a commanding officer would initiate the procedure by requiring his or her helmsperson to "plot an intercept course."
In 2267, Lieutenant Hikaru Sulu, while helming the USS Enterprise, plotted an interception course towards a Federation ship under Klingon attack. He did so under Commander Montgomery Scott's orders, even though it meant leaving behind an Enterprise landing party on the planet Capella. (TOS: "Friday's Child")
Perhaps the most infamous series of intercept courses in Starfleet history occurred in 2367. In that year, Admiral Hanson ordered dozens of vessels, Starfleet and Klingon alike, to intercept the Borg at Wolf 359. His hope was that by making a stand there, Earth could be better defended. Unfortunately, the plan failed. Almost none of Hanson's fleet survived the encounter. (TNG: "The Best of Both Worlds", "The Best of Both Worlds, Part II")
In 2374, Romulans who had taken over the USS Prometheus noted that Starfleet vessels were on an incercept course that was materially created by the Prometheus' un-masked warp trail. (VOY: "Message in a Bottle") Later that year, an Hirogen hunter made the point of an intercept course entirely explicit when he remarked to a colleague, "The prey's course has become erratic. I will intercept to kill." (VOY: "Prey")