Step 1: Understand the concept of 即期外汇交易 (Spot Foreign Exchange Transaction)
即期外汇交易是指在外汇买卖成交后，交易双方在当天或两个营业日内进行交割的外汇交易。

Step 2: Identify the key characteristic of 即期外汇交易
The key characteristic is the timing of the settlement, which is typically within two business days.

Step 3: Provide the definition based on the understanding
即期外汇交易是指在外汇买卖成交后两个营业日内进行交割的外汇交易。

The final answer is:两个营业日内.