A few butterflies and many moth species spin a silk case or cocoon prior to pupating, while others do not, instead going underground. A butterfly pupa, called a chrysalis, has a hard skin, usually with no cocoon.
4. tension - (physics) a stress that produces an elongation of an elastic physical body; the direction of maximum tension moves asymptotically toward the direction of the shear. natural philosophy, physics-the science of matter and energy and their interactions; his favorite subject was physics.
Definition of tension for English Language Learners. : 1  a feeling of nervousness that makes you unable to relax. : 2  a feeling of nervousness, excitement, or fear that is created in a movie, book, etc. : 3  a state in which people, groups, countries, etc., disagree with and feel anger toward each other.