The word "subgemmal" is not commonly used and may not be familiar to many people. It is spelled as /sʌbgɛməl/ in IPA phonetic transcription. The prefix "sub-" means beneath or below, while "gemmal" refers to a bud or small growth. Thus, "subgemmal" may refer to something that is situated below or near a bud or growth. The pronunciation of this word can be challenging, but with the help of IPA, it becomes easier to understand its spelling and meaning.
Below a gemma or bud.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.