Here are our top 20 adjectives that start with the letter R: Rabid - extreme; fanatical. Radiant - emanating light or joy. Radical - far-reaching; revolutionary. Radioactive - emitting radiation. Rakish - dashing, yet slightly disreputable. Rambunctious - being wild and disorderly. Rampant - spreading uncontrollably. positive words that start with r - A comprehensive listing of positive words that start with r and their definitions.