Is there also a Spanish word for chairman? The ones I have seen for chairman are "presidente" but that doesn't make sense to me because I immediately think of the word president instead of chairman.
The translation is "presidente" for most cases, but in few contexts you may look up the exact term. Looking at the definition, you can see that "presidente" covers anybody that is the head or leader of boards, clubs, associations..., not being important the size of the board or the powers and duties he/she may have.
About the gender agreement, the recommended form for both men and women is "presidente" (el presidente, la presidente) as in others words ended in "-ente", but it is widely used as well "la presidenta".