There are two kinds of English-English dictionaries: dictionaries for learners and dictionaries for native speakers. Dictionaries for native speakers are used by Americans, Britons, etc. to look up rare words, such as inextricable ____ tintinnabulation. Dictionaries for learners are used by people who are learning English as a second language.
As for the usage of coordinating conjunctions, which one fits the blank space better? I prefer “or” because it suggests that there are many more possibilities than the two mentioned.
Both are possible, but I agree with you that "or" sounds better: the words provided are only two examples among the countless terms that can be looked up in a dictionary, and the use of "or" is indicative of the length of that list of words.