PROTACTINIUM /ˌpɹəʊ.tækˈtɪn.i.əm/ Scrabble 18 Words With Friends 23 Definition noun a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead. — synonyms: protoactinium, Pa, atomic_number_91 See all 651 words you can make from PROTACTINIUM → 12-letter words Words starting with P Words ending with M ← Unscramble different letters