According to our high school Biology book and several web-sites, "thigmotropism is the directional response of a plant organ to a touch or physical contact with any solid object. The response is usually caused by the adding of some pattern of differential growth." Thigmotropism can be seen in the climbing tendrils of some plants, such as morning glories or climbing roses. The tendrils actually "feel" the pole or object they come into contact with, and this pressure results in a coiling response around the pole or the object those tendrils come into contact with.
Thigmotropism is the tropic movement in the plants due to the stimulus of touch, tactile, mechanical or rubbing. The response is generally positive in stem of climbers and in tendrils causing them to twin round the support. The first response, which occurs within a few seconds after perceiving the stimulus, is the contraction of the cells towards the side of stimulus, with the results cells become concave. Simultaneously, the cells expand on the opposite side. The growth rate increases 40-200 folds on convex side, whereas on concave side the growth rate becomes slow or stops.
Tropisms are the response of a plant to something in its natural environment. Thigmotropism, in particular, is a general term used to describe a plant's response to physical contact.