It might be easiest to define a liberal arts education by defining the two things it isn’t:
1) It isn’t career training. If there is a promise–even implicitly–that a college education will prepare you for a career then it isn’t a liberal arts education.
2) It isn’t research. If faculty are primarily incentivized by scholarly output then it isn’t a liberal arts education.
An institution can seek to serve all three of these missions–liberal arts, career training, and research–but it cannot serve them all well without vast sums of money.