Trending Undercut Hairstyle Undercut Designs Lines : The undercut is a hairstyle that was fashionable from the 1910s to the 1940s, predominantly among men, and saw a steadily growing revival in the 1980s before becoming fully fashionable again in the 2010s. The disconnected undercut hairstyle has been a major trend these past few years. Undercut Hairstyle Undercut Designs Lines : These days, it's turned into a trendy hairstyle that be worn anytime.