Mega/ˈmeɡə/ Definition 1 of 3Pro Tip 1/3Scale Indicator Mega as a prefix suggests something is large enough to be impressive or noteworthy. That construction is a megastructure. Pro Tip 2/3Technology Related When talking about technology, 'mega' often relates to digital storage and processing. This file is 5 megabytes. Pro Tip 3/3Formal Speech 'Mega' is more casual; use alternatives like 'extremely large' for formal writing. We secured a megacontract with the company.