Correct spelling for the English word "subgrundation" is [sˌʌbɡɹəndˈe͡ɪʃən], [sˌʌbɡɹəndˈeɪʃən], [s_ˌʌ_b_ɡ_ɹ_ə_n_d_ˈeɪ_ʃ_ə_n] (IPA phonetic alphabet).
The depression of one fragment of a broken cranial bone below the other.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.