I cut my eyebrow with scissors. Will it grow back if I just leave it alone?

Eyebrow trimming does not effect eyebrow hair growth.  Removing eyebrow hairs from the root, such as waxing, plucking, etc.  Best Dr. Anil Shah

Yes, this may grow back in time, provided you did not cut the roots. Prp and progesterone can help regrow the eyebrows. I recommend getting a consultation with a hair growth expert. Best, Dr. Emer

As opposed to repeated plucking, just trimming the eyebrows should not have any long-term effects on their growth

Trimming hair has no effect on its growth. Your eyebrow growth rates and growth patterns will not be affected by the trimming and will grow as they did before. It will simply take a few weeks.

I have heard that in a few occasions, that some people cut their eyebrow hairs at the roots and it did not come back.  You will know in 6 months which is the longest cycle I know of