Underrate, v. t.
To rate too low; to rate below the value; to undervalue. Burke.
1 other Webster entry under this spelling
Underrate, n.
A price less than the value; as, to sell a thing at an underrate. Cowley.
Shades of meaning
Fernald has no entry of its own for underrate; he lists it under disparage.
Where he writes about it:
A witness or a statement is discredited; the currency is depreciated; a good name is dishonored by unworthy conduct; we underestimate in our own minds; we may underrate or undervalue in statement to others. — from disparage