was about toUsually used as part of the construction s'apprêter à + infinitive, meaning to be about to do something or to be preparing to do it. The form apprêtais is the imperfect first-person singular form; other forms include s'apprête à (is about to) and s'apprêtait à (was about to).
FR: Je m'apprêtais à sortir quand il a commencé à pleuvoir.
EN: I was about to go out when it started to rain.