Correct spelling for the English word "megalopenis" is [mˈɛɡəlˌə͡ʊpniz], [mˈɛɡəlˌəʊpniz], [m_ˈɛ_ɡ_ə_l_ˌəʊ_p_n_i_z] (IPA phonetic alphabet).
Abnormal size of the penis, macrophallus.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.