flavourless

adjective3

1. •
   Lacking taste or flavor; without seasoning, spice, or discernible qualities of taste.

   • Salt oysters, on being transferred to fresh water, are "fattened" in the course of two or three days ; if allowed to remain longer they become lean again, and are flavorless. — 1876
2. •
   Flat; lacking character or definition.

   • […] and the gravestone of its dead owner on the hill was no more flavorless of his personality than was this plain house in which he had lived and died. — 1902
3. •
   Without flavor.

   • On the other hand, Pauli had just proposed a massless, chargeless, colorless, flavorless particle whose sole reason for existence was to preserve the principle of momentum conservation. — 2014