Moving Part of a Reciprocating Engine
This page is the CodyCross answer for the clue below from Forests, Group 1991, Puzzle 4 (Soil Composition).
Question is: Moving Part of a Reciprocating Engine
and the answer is: PISTON
Word Meaning:
PISTON — (mechanics) A solid disk or cylinder that fits inside a hollow cylinder, and moves under pressure (as in an engine) or displaces fluid (as in a pump)
Definitions from Wiktionary.