The superlative form of busy; most occupied with activity or having the most things to do.
From Old English 'bisig' meaning 'careful' or 'attentive,' possibly related to 'business.' The -est suffix makes it the superlative form. The modern sense of 'having lots to do' developed from the original meaning of being mentally occupied.
Psychologically, research shows that busy people often overestimate how much they accomplish while underestimating their actual free time—it's called the 'busy-ness bias.' The busiest people aren't necessarily the most productive; they just feel like they are because switching between tasks is exhausting!
Complete word intelligence in one call. Free tier — 50 lookups/day.