A business or individual that undertakes work for another company under a contract, often in construction, manufacturing, or IT.
Several subcontractors are involved in this project.
The major construction company uses many subcontractors.
元請け is the prime contractor who directly receives the order from the client, while 下請け業者 is the subcontractor who works under the prime contractor.
Compound of 下請け (したうけ, 'subcontract') + 業者 (ぎょうしゃ, 'business operator').