Today, a standard bitcoin transaction records both transaction and signature data together, with the signatures accounting for approximately 60 % of the data size. (coindesk.com)
«SegWit» is an abbreviation for «segregated witness», which is the process whereby a blockchain's block size limit is increased by removing signature data from transactions. (chainbits.com)
SegWit is the process by which the block size limit on a blockchain is increased by removing signature data from Bitcoin transactions. (investopedia.com)