GRIEVOUSLY Copy link • GRIEVOUSLYgraviter: vehementer: acerbe: acriter: atrociter: foede or foedum in modum: dolenter [SYN. in GRIEVOUS]: terribilem or horrendum in modum (terribly). To be grievously ill, graviter aegrotare: to be grievously mistaken, valde or vehementer errare (☞ not toto caelo errare; Vid: “to be GREATLY mistaken.