The markets are not robust

Yesterday the US equity markets took a dive. The second largest one-day point drop in history is now being attributed to trader error.

From Merriam-Webster

Main Entry: ro·bust
Pronunciation: \rō-ˈbəst, ˈrō-(ˌ)bəst\
Function: adjective
Etymology: Latin robustus oaken, strong, from robor-, robur oak, strength
Date: 1533

1 a : having or exhibiting strength or vigorous health b : having or showing vigor, strength, or firmness c : strongly formed or constructed : sturdy d : capable of performing without failure under a wide range of conditions

With all the fail-safes in place…for that matter all the potential buyers in place, it happened.

Buy or sell, you’d like a robust market. Do you really think this one fits the definition?