ɪnfˈɔːɹməli, ɐ plˈeɪɚ plˈeɪɪŋ baɪ ɐ stɹˈæɾədʒi fɹʌm ɐ kwˈeɪzaɪpˈɜːfɛkt ˌiːkwɪlˈɪbɹiəm tˈeɪks əbzˈɜːvd æz wˈɛl æz pətˈɛnʃəl fjˈuːtʃɚ mɪstˈeɪks ʌv hɪz əpˈoʊnənts ˌɪntʊ ɐkˈaʊnt bˌʌt ɐsˈuːmz ðæt hiː hɪmsˈɛlf wɪl nˌɑːt mˌeɪk ɐ mɪstˈeɪk ɪnðə fjˈuːtʃɚ, ˈiːvən ɪf hiː əbzˈɜːvz ðæt hiː hɐz dˈʌn sˌoʊ ɪnðə pˈæst.
Informally, a player playing by a strategy from a quasi-perfect equilibrium takes observed as well as potential future mistakes of his opponents into account but assumes that he himself will not make a mistake in the future, even if he observes that he has done so in the past.