(idiomatic) The part of a tool or weapon that is physically used for its operation, rather than the part which is held.

(physics) The conversion of one form of energy into another, or the movement of energy from one place to another.

Just the right amount is as good as more than enough: there is no value in excess.

To turn (something) upside down, to invert (something).

Epithet for World War I.

Any of several internal combustion engines that have the cylinders arranged radially around a central crankshaft

Non-polluting source of energy.

last remnant / frayed end of a length of cloth or rope / The unsmoked end of a cigarette or cigar

A form of jet engine that possesses an inlet duct, such as a turbojet, ramjet, or turbofan. Rockets are not considered duct engines.

Alternative form of be-all and end-all