So-called “short a”

The so-called “short a” sound is an informal term that means the short sound of the letter a which is IPA phoneme  (for a North American accent see Phoneme /æ/ in General American).

Examples
 * In all the English speaking world: trap - have - rapid - battle
 * In General American the following examples can be added: after - ask - bath - can't - last
 * In Received Pronunciation we can say that these words (which sound /ɑː/) have “short a” spelling.

The terms “long a” and “short a” are not recommended because the opposition between /æ/ and /eɪ/ (“long a”) is not only a difference in length, but mainly a difference in quality.