PROTEROZOIC EON

\pɹˈə͡ʊtɹəzˌə͡ʊɪk ˈiːɒn], \pɹˈə‍ʊtɹəzˌə‍ʊɪk ˈiːɒn], \p_ɹ_ˈəʊ_t_ɹ_ə_z_ˌəʊ_ɪ_k ˈiː__ɒ_n]\
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2006 - WordNet 3.0
By Princeton University
 
2011 - English Dictionary Database
By DataStellar Co., Ltd