|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.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
methylene meth·yl·ene (měth'ə-lēn')
A bivalent hydrocarbon radical, CH2, that is a component of unsaturated hydrocarbons and is derived from methane by the removal of two hydrogen atoms.
|methylene (měth'ə-lēn') Pronunciation Key
A bivalent hydrocarbon radical, CH2. Because it has two unshared electrons, it is extremely reactive and occurs only as an intermediate byproduct in chemical reactions. Methylene is a component of unsaturated hydrocarbons.