A layoff is a reduction in force, ie we need to lower headcount by 10% so bring me 10 names at this 100 person company. Firing someone for performance/attitude/don't-like-you-anymore reasons isn't a layoff.
I don't think that's right. I know as a fact that when Facebook did their layoffs here in UK they got rid of their lowest performing employees, going through the proper multi-month process, but at the end of the day they got rid of a large percentage of their staff purely based on merit/performance. I literally don't see how that's not a layoff.
