Is it permissible for spouses to use descriptive words for genitalia, or obscene words, for the purpose of arousal during marital intimacy, taking into account the Prophet's (peace and blessings be upon him) dislike of obscene language, or does this fall under what is forbidden in marital relations?

A Muslim should be chaste in their actions and words. If one is compelled to mention something that might cause embarrassment in order to achieve a legitimate objective, then there is no harm in that, as the Prophet, peace and blessings be upon him, did on some occasions. However, if there is no need for it, and the words are not forbidden, then it is preferable not to state them explicitly and doing so would be considered reprehensible (makrooh). Therefore, there is no harm in saying what was mentioned in the question, provided it does not extend beyond the spouses to their children or others.