Other forms: jerkier; jerkies
Something that's jerky has a bumpy, lurching kind of rhythm, like a jerky off-road ride in a jeep. Another kind of jerky is dried meat. You could chew your beef jerky to calm yourself on that jerky ride.
A jerky carnival ride starts and stops abruptly, and a jerky old movie might be choppy and shaky. When jerky is a noun, it's a dense, chewy type of dried meat. This second kind of jerky is an American word, adapted from the Spanish to originally be charqui, from an Incan root word, ch'arki, literally "dried flesh."