1. [adj]  (of a boat or vessel) furnished with necessary official documents specifying ownership etc
2. [adj]  listed or recorded officially; "record is made of `registered mail' at each point on its route to assure safe delivery"; "registered bonds"
3. [adj]  (of animals) officially recorded with or certified by a recognized breed association; especially in a stud book; "a registered Percheron"

REGISTERED is a 10 letter word that starts with R.