exclamation point (!): also called "exclamation mark".

exclamation point (!) [1]: a symbol which is attached to the beginning of a linguistic form to indicate that it is especially preferable, acceptable, or correct, especially in a series of alternatives. For example, one could list alternative past tense forms of the verb "think" as "*thinked", "??thunk", "?thot" and "!thought". (This use of the exclamation point can be found in some of the same contexts as the second use below, which can cause confusion. Thus, it is important to notice how a particular author proposes to use it.) Compare asterisk [1] (*), question mark [1] (?). [Spanish: signo de admiración [1]]

exclamation point (!) [2]: a symbol which is attached to the beginning of a linguistic form to indicate that it is syntactically well-formed but semantically ill-formed. As a famous example, "!Colorless green ideas sleep furiously" is considered correct in its grammatical form but anomalous in its meaning. (This use of the exclamation point can be found in some of the same contexts as the first use above, which can cause confusion. Thus, it is important to notice how a particular author proposes to use it.) Compare asterisk [1] (*), question mark [1] (?). [Spanish: signo de admiración [2]]

exclamation point (!) [3]: a symbol which is used with phonological features to indicate a feature whose presence facilitates a phonological process, even though it is not required. For example, [+high, !anterior] means that for a phonological process to operate, the segment referred to must be high [1], and if it is also front (anterior), this is the preferred case. Compare plus sign [1] (+), minus sign (). [Spanish: signo de admiración [3]]