This relates to how you respond when put under pressure. In a work context, pressure can be defined as:
“The stress or urgency of matters requiring attention, the burden of physical or mental distress and the constraint of circ*mstances.”
The ability to work under pressure involves dealing with constraints which are often outside of your control - these might be resource or time constraints, the difficulty of the task or having insufficient knowledge required to complete the task, or unforeseen changes or problems. Effective planning and time-management (to mitigate or allow for unexpected problems for example) can reduce the likelihood of some pressurised situations occurring, but will not eradicate them completely.