undersay

verb2

1. •
   To understate.

   • My words undersay it, of course; I mean something rarer than critical, something better than ethical, and perhaps I had better retreat upon such a word as spiritual. — 1899
2. •
   (no longer used) To say by way of derogation or contradiction.

   • They say, they con to heaven the highway; But by my soul I dare undersay, They never set foot on that same troad, But balke their right way, and strayen abroad. — 1579