sparerule

noun
UK /ˈspɛəruːl/
US /ˈspɛrruːl/

A sparerule is an extra rule you can use when you need one.

The teacher kept a sparerule in her desk for special games.


OTHER MEANINGS

2. A rule kept in reserve in case the main rule fails.

If the first rule breaks, the sparerule takes over.

3. An additional rule added to a game for fairness.

They added a sparerule so everyone got a turn.

4. A spare part shaped like a ruler.

He used a sparerule to fix the broken shelf.