undertakingun·der·tak·ing /ˌʌndəˈteɪkɪŋˈʌndərteɪ-/ noun1[countableC usually singular] an important job, piece of work, or activity that you are responsible forStarting a new business can be a risky undertaking.
2[countableC]COMMERCE a businessThe railway’s commercial undertaking was divided into its separate elements.
the parent company and its subsidiary undertakings
3[countableC] a promise to do something, especially one that has legal forceHe gave an undertaking that he would repay the money in full.