ambitious undertaking; grand scheme
Refers to a large-scale, bold plan or project. Somewhat literary and not an everyday word; often used in written or formal contexts.
He had harbored an ambitious undertaking since his youth.
That plan can truly be called a grand national scheme.
Compound of 壮 (grand, magnificent) and 図 (plan, scheme). The exact historical derivation is uncertain, but the word is conventionally associated with large-scale, bold plans.