adv. 25B6; adverb
he is mightily impressive : EXTREMELY, exceedingly, enormously, immensely, tremendously, hugely, dreadfully, very (much); informal awfully, majorly, mega; N. Amer. informal mighty, plumb; informal, dated devilish.
Ann and I laboured mightily : STRENUOUSLY, energetically, powerfully, hard, with all one's might, with might and main, all out, heartily, vigorously, diligently, assiduously, persistently, indefatigably; informal like mad, like crazy; Brit. informal like billy-o.