monoplane adjective 1noun 1verb 1forms 3 adjective1 •Composed of, or relating to, a single plane (flat surface extending infinitely in all directions). noun1 •An airplane that has a single pair of wings.By the mid-1930s, designs for new fighters and bombers were almost all monoplane designs. verb1 •(rare) To fly in a monoplane. formsmonoplaned · monoplaning · monoplanes