from
The Collaborative International Dictionary of English v.0.48
Semi-Diesel \Sem`i-Die"sel\, a.
Designating an internal-combustion engine of a type
resembling the Diesel engine in using as fuel heavy oil which
is injected in a spray just before the end of the compression
stroke and is fired without electrical ignition. The fuel is
sprayed into an iron box (called a hot bulb or hot pot)
opening into the combustion chamber, and heated for ignition
by a blast-lamp until the engine is running, when it is,
ordinarily, kept red hot by the heat of combustion.
[Webster 1913 Suppl.]