In SRE, we want to spend time on long-term engineering project work instead of operational work. Because the term operational work may be misinterpreted, we use a specific word: toil.
Toil is the kind of work tied to running a production service that tends to be manual, repetitive, automatable, tactical, devoid of enduring value, and that scales linearly as a service grows.
Note: less toil is better. Most of an SREs work should be to reduce future toil or add service features.