mathematics The most common norm, calculated by summing the squares of all coordinates and taking the square root. This is the essence of Pythagoras's theorem. In the infinite-dimensional case, the sum is infinite or is replaced with an integral when the number of dimensions is uncountable. (2004-02-15)
a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.
a chattering or flighty, light-headed person.
a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question.
a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.