Diesel motor and Internal-combustion engine

Diesel motor noun - An internal-combustion engine that burns heavy oil.

Internal-combustion engine and diesel motor are semantically related. In some cases you can use "Internal-combustion engine" instead a noun phrase "Diesel motor".

Internal-combustion engine noun - A heat engine in which combustion occurs inside the engine rather than in a separate furnace; heat expands a gas that either moves a piston or turns a gas turbine.

Diesel motor and internal-combustion engine are semantically related. Sometimes you can replace phrase "Diesel motor" with "Internal-combustion engine", this phrases are similar.