The phrase "significant underperformance" means that someone or something is performing much worse than expected or compared to others in a noticeable way. Full definition
Even superstar fund managers with brilliant track records can hit a streak of significant underperformance. (newconstructs.com)
We strongly believe that when the overall market rebounds, small - cap shareholders will experience significant underperformance unless their boards effect a change - of - control transaction. (greenbackd.com)
New study shows calling children «average» hides their problems and potential and could lead to significant underperformance in GCSE exams (qaeducation.co.uk)