schwa The mid-central vowel of e.g. the second syllable of matter: in phonetic notation [ ə ] ([matə ]) . Also spelled 'shwa'.
selective listening Selective attention to an individual speaker, e.g. in a crowded room where many people are talking.
shifter Jakobson's term for words like I, you and others whose interpretation involves person deixis.
speech error An accidental error in speech: cf. slip of the tongue.
Definitions from: The Concise Oxford Dictionary of Linguistics, Second edition, 2007
Image credits: Wikipedia - Braille representation of letter 'S'