The most common crossword answer for the clue "old Celtic priest" is the word DRUID , which has 5 letters. This is the widely accepted solution for various crossword puzzles, including major publications like the LA Times and the New York Times.

Summary of Answers

• DRUID (5 letters) — the principal and most frequent answer for "old Celtic priest"
• Plural form DRUIDS (6 letters) is also used for "Celtic priests" in plural

Thus, if the crossword clue is "old Celtic priest," the best fit answer is almost certainly DRUID.