Other forms: middlebrows
A middlebrow is someone whose tastes are neither highbrow nor lowbrow. They're somewhere in between.
A highbrow is someone with classy, sophisticated tastes. A lowbrow is someone with vulgar, uncultured tastes. A middlebrow, therefore, is someone with tastes that fall somewhere in the middle. A middlebrow might enjoy both lowbrow and highbrow entertainment, such as the rodeo or the opera. Or they might enjoy things that fall smack in the middle as far as sophistication goes. If you like art that's about halfway between classy and trashy, you might be a middlebrow.