Definition of "top-up"

top-up

adjective
not comparable
1. That serves as an addition
noun
countable and uncountable, plural top-ups
1. An addition.
  Quotations
  Energy will be generated from solar panels, water will be recycled and extracted from soil and the astronauts will grow their own food - they will also have an emergency ration and regular top-ups as new explorers join every two years.
  2013, Melissa Hogenboom, “Applicants wanted for a one-way ticket to Mars”, in BBC News
2. A serving of drink used to top up an existing glass.
3. (insurance) An additional premium paid over the initial premium in order to increase benefit values.
4. Additional credit purchased for a mobile phone.
5. (medicine) A dose of epidural anesthetic added to previously injected spinal anesthetic in combined spinal-epidural anesthesia
  Quotations
  The reinforcement of anesthesia by an epidural “top-up” in combined spinal-epidural anesthesia may be explained by a dual mechanism: a volume effect compressing the dural sac and a local anesthetic effect.
  1999, The Epidural “Top-Up” in Combined Spinal-Epidural Anesthesia: The Effect of Volume Versus Dose‎
6. (education) The situation where a student who holds a qualification equivalent to part of a degree course is then accepted onto a degree course at an intermediate point, without having to start it from the beginning.