The idiom “plunging into the unknown” refers to venturing into a situation with uncertainty or little knowledge about the outcome. A person rides their bike down an unfamiliar trail, loses control, and falls, hitting their head. Someone might say, “They really plunged into the unknown without knowing what was ahead.” A company invests in a new, untested market with no guarantee of success. You could say, “Launching in that region was like plunging into the unknown, but it paid off in the end.” L