Countable: a drink, snack, or short period before lunch.
Let's have a pre-lunch before heading to the restaurant.
Давай выпьем аперитив перед тем как пойти в ресторан.
Used attributively to describe events or periods occurring before lunch.
The pre-lunch meeting lasted an hour.
Предобеденное совещание длилось час.
Modifies a verb or clause to indicate that the action happens before lunch.
They went over the figures pre-lunch.
Они обсудили цифры до обеда.