For the similarly-named artistic style, please see realism.
A realist was someone who saw things as they were, rather than better (optimism) or worse (pessimism). A realist was typically considered the opposite of an idealist.
In 2376, when discussing whether Liam or Harry Kim would emerge victorious in an arm wrestling competition, "Katie O'Clare" expressed her belief that Kim would win, despite Michael Sullivan noting that nobody had beaten Liam in three years. When Michael suggested "Katie" was an optimist, she countered that she was a realist. (VOY: "Fair Haven")