Is it permitted for a male to trim body hair eg chest/abdomen/armpit?
Hair removal from parts of the body which are generally only done by women is prohibited, even if it is bothersome. Chest hair which is exclusive to men may be trimmed, without a razor. Only when hair growth is causing a medical issue or great embarrassment may it be removed, in a way otherwise prohibited.
Shulchan Aruch Yoreh Deah 182