What term describes the position of the piston when it is at the lowest point in its movement?

The term that describes the position of the piston when it is at the lowest point in its movement is known as Bottom Dead Center (BDC). At this point, the piston is furthest away from the cylinder head, marking the end of the downward stroke in a reciprocating engine cycle. Understanding the significance of this position is crucial, as it is essential for various engine processes, including the intake of air-fuel mixture or exhaust gases, depending on the engine's operating phase.

Top Dead Center (TDC) refers to the opposite position, where the piston is at its highest point, while the compression stroke and exhaust stroke refer to specific phases of the engine cycle rather than the position of the piston. Therefore, BDC is the correct terminology for the lowermost position of the piston.