lobster thermidor Syllabification: (lob·ster ther·mi·dor)Pronunciation: /ˈTHərməˌdôr/Definition of lobster thermidor noun a dish of lobster cooked in a cream sauce, returned to its shell, sprinkled with cheese, and browned under the grill. Origin:thermidor from Thermidorlobster thermidor in other Oxford dictionaries Definition of lobster thermidor in the British & World English dictionary