n. In horticulture: A trelliswork of various forms on which the branches of fruit-trees or -bushes are extended horizontally, in fan shape, etc., in a single plane, with the object of securing for the plant a freer circulation of air as well as better exposure to the sun.n. A tree or plant trained on such a trellis or system. Trees trained as espaliers are not subjected to such abrupt variations of temperature as wall-trees.To train on or protect by an espalier, as a tree or trees.