I. ˌRegistered ˈNurse BrE AmE abbreviation , RN noun
a nurse who is fully trained and has passed all the necessary exams. A registered nurse has a higher qualification than an ENROLLED NURSE (in the UK) or a LICENSED PRACTICAL NURSE (in the US).
II. RN /ˌɑːr ˈen/ BrE AmE
1 . the abbreviation of registered nurse
2 . British English the abbreviation of Royal Navy :
Captain Anstruther, RN