1. Spend less than the whole of (a budget, for example)
   "The school underspent its technology budget this year"; "The marketing team underspent on the campaign"
    
2. Spend at less than the normal rate
   "The department underspent its budget this quarter"; "They underspent on advertising, which affected their sales"

Derived forms: underspending, underspends, underspent

Type of: drop, expend, spend

Antonym: overspend