trunk engine

noun

1

: a steam engine having a piston rod that is a pipe of sufficient diameter to enable one end of the connecting rod to be attached to the crank and the other end to pass within the pipe and be pivoted to the piston

2

: an engine (as most internal-combustion engines) having a trunk piston

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!