1. A call or greeting, informal. An acknowledgement of notice.
2. A more formal or greater acknowledgement or greeting than aru.
3. An acknowledgement response to aru.
*** BetterThanJoe just entered the room.
Kerr: Aruga, BetterThanJoe!
*** JoeBob just entered the room.
Kerr: Aru, JoeBob.
when you see a good-looking girl/guy. you say "aruga".
"aruga" the guys says.