A strong acid is one that completely dissociates in water; in other words, one mole of a strong acid HA dissolves in water yielding one mole of H+ and one mole of the conjugate base, A−, and none of the protonated acid HA.
ɐ stɹˈɔŋ ˈæsɪd ɪz wˈʌn ðæt kəmplˈiːtli dɪsˈoʊsɪˌeɪts ɪn wˈɔːɾɚ; ɪn ˈʌðɚ wˈɜːdz, wˈʌn mˈoʊl əvə stɹˈɔŋ ˈæsɪd ˌeɪtʃˈeɪ dɪsˈɑːlvz ɪn wˈɔːɾɚ jˈiːldɪŋ wˈʌn mˈoʊl ʌv ˈeɪtʃ plˈʌs ænd wˈʌn mˈoʊl ʌvðə kˈɑːndʒuːɡˌeɪt bˈeɪs, ɐ mˈaɪnəs, ænd nˈʌn ʌvðə pɹˈoʊtənˌeɪɾᵻd ˈæsɪd ˌeɪtʃˈeɪ.