Strongest of all
Robustest is the superlative form of robust, meaning most sturdy, healthy, or vigorous.
While grammatically valid, it sounds awkward to most English speakers, who prefer most robust: She had the most robust immune system in the family.
Robustest occasionally appears in informal or playful contexts.
IDEA.org / Words / robustest
Strongest of all
Robustest is the superlative form of robust, meaning most sturdy, healthy, or vigorous.
While grammatically valid, it sounds awkward to most English speakers, who prefer most robust: She had the most robust immune system in the family.
Robustest occasionally appears in informal or playful contexts.
1. superlative — strongest, Maximum in power; sturdiest (Most solidly constructed); toughest (Most difficult or resilient); hardiest (Most resistant to adversity); healthiest · soundest
physical strength and constitutionrobustest ≠ weakest Least strong or capable; frailest · feeblest · puniest · fragilest · wimpiest
health and vitalityrobustest ≠ sickliest Superlative of unwell; unhealthiest · frailest
system or design resiliencerobustest ≠ flimsiest Least substantial or sturdy; fragilest · weakest · shakiest · ricketiest · faultiest
robust, robustness, robustly
Word data: Linguabase (CC0) · www.idea.org/words/robustest