™A 500-share fill-or-kill instruction seeks an immediate complete execution under its conditions; available partial size does not satisfy the whole instruction.
Orders & Market Structure
Fill-or-kill order (FOK)
An order requiring immediate complete execution or immediate cancellation.
Plain-English context
Put the definition to work.
Immediate full execution is a condition of the instruction, not a guarantee that enough compatible liquidity exists.
Further reading and verification. Examples are hypothetical, not current quotes or recommendations. Product terms, tax treatment and market rules can change. FINRA — order types and execution