means The combined effort of a group working together toward a shared goal, where the contributions of many add up to more than any one person could manage alone.

from A straightforward compound of "team" and "work." "Team" is the older word, from Old English "team," which first meant a set of draft animals harnessed together to pull a load — oxen yoked to drag the same cart in the same direction. That sense of bodies bound to a common pull eventually stretched to cover people. "Teamwork" itself is a much later, plainspoken pairing, an 19th-century coinage that began literally — the coordinated labor of a team of animals — before being borrowed for the human kind of pulling together.