Yes, hair from your arm pit can be used for an eyebrow transplant. You need to find a doctor who specializes in this area and get that doctor to agree with you on the donor supply
The long and short answer is that yes, armpit hair could possibly be used as donor hair. However, it is not the best choice by any means. The hairs are different so they will look unnatural once in the eyebrows and they will also not be a very permanent solution to replace the hair that has already been lost in this area. Choosing the donor hair from the back of the scalp is a much better solution and it is also important to make sure to use the proper grafts implanted at the proper angles so that the result looks natural.