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.
The definition of tighten is to make something more fixed in place, more constricted, or more snug. 1  To turn the lid on a jar is an example of tighten. 2  To cut back on spending is an example of tighten a budget.  To tailor a shirt to fit more closely is an example of tighten.