Step 1: Go back to the source of the definition.
The Coal Mines Regulations, 2017 define a misfire under Regulation 2(1)(zd) as the failure to explode of the whole or part of a charge of explosive in a shot hole.
Step 2: Note that this covers two situations.
So technically the official wording covers both a complete failure, where none of the charge goes off, and a partial failure, where only some of the charge fails to detonate, both fall under the umbrella term misfire.
Step 3: Match this to the closest listed option.
Among the choices given, options about "failure of ignition" or "improper ignition" describe possible causes rather than the outcome itself, while the option describing failure of the entire charge captures the core, most commonly tested meaning of a misfire as the charge simply not going off as intended.
Step 4: Conclude.
So the meaning of misfire, as intended by the answer key, is the failure to explode the entire charge of explosive.
\[ \boxed{\text{Failure to explode entire charge of Explosive}} \]