Is all forms of nsu consider a std or is that just if it is caused by chlamdyia etc?since i passed two std tests meaning i'm clean can i pass it on?

Not STD: It can be caused by mycoplasma or urea plasma or several other organisms. If you still have it you need a culture and treatment. It can be transmitted sexually although it is not on the usual list of STDs. In other words it is sexually transmissible but not necessary sexually transmitted.

NSU is an STD: Nonspecific urethritis (NSU), the usual name in many countries, is the same as nongonococcal urethritis (NGU) as its usually called in No. America. It's an STD, with maybe a few exceptions. Chlamydia causes about one third of cases; the rest have other or unknown causes. Even with negative STD tests, you may be able to infect partners. You need to be treated and so do they.