Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure. It is an amorphous material known as a  mineraloid .. The result is a volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture (see photo on right). Obsidian is usually an extrusive rock-one that solidifies above Earth's surface. However, it can form in a variety of cooling environments: Black is the most common color of obsidian.
â¢ PEP TALK (noun). The noun PEP TALK has 1 sense: 1. a speech of exhortation attempting to instill enthusiasm and determination in a team or staff. Familiarity information: PEP TALK used as a noun is very rare.
noun, plural peplums, pepla. [pep-luh] /ËpÉp lÉ/ (Show IPA) 1. a short full flounce or an extension of a garment below the waist, covering the hips. 2. a short skirt attached to a bodice or jacket. 3. Obsolete. a peplos. Origin of peplum.