There are 10 13-letter words that start with 'ru'.
| rubberneckers | rubbernecking |
| rubicundities | rudimentarily |
| ruggedization | ruinousnesses |
| rumbustiously | rutherfordium |
| ruthfulnesses | ruttishnesses |
Note: These 10 13-letter words that start with 'ru' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with rub, rum, rus, run, rud, rug, rut, ruf, ruc, rur, rui, rul, rue, rup, rua.
3-letter words start with 'ru' (6)