Unaccomplishment (n.)
definition: The state of being unaccomplished.

Unaccomplishment is a 16 letter word that begins with a U and ends in a T

Unaccountability (n.)
definition: The quality or state of being unaccountable.

Unaccountability is a 16 letter word that begins with a U and ends in a Y

Unacquaintedness (n.)
definition: Unacquaintance.

Unacquaintedness is a 16 letter word that begins with a U and ends in an S

Unconstitutional (a.)
definition: Not constitutional; not according to
Or consistent with the terms of a constitution of government; contrary to the constitution; as an unconstitutional law or act of an officer.
Unconstitutional is a 16 letter word that begins with a U and ends in an L

Uncontrovertible (a.)
definition: Incontrovertible.

Uncontrovertible is a 16 letter word that begins with a U and ends in an E

Uncontrovertibly (ad)
definition: Incontrovertibly.

Uncontrovertibly is a 16 letter word that begins with a U and ends in a Y

Underchamberlain (n.)
definition: A deputy chamberlain of the exchequer.

Underchamberlain is a 16 letter word that begins with a U and ends in an N

Underconsumption (n.)
definition: Consumption of less than is produced; consumption of less than the usual amount.

Underconsumption is a 16 letter word that begins with a U and ends in an N

Undifferentiated (a.)
definition: Not differentiated; specifically (Biol.)
Homogenous or nearly so; -- said especially of young or embryonic tissues which have not yet undergone differentiation (see Differentiation 3) that is which show no visible separation into their different structural parts.
Undifferentiated is a 16 letter word that begins with a U and ends in a D

Unextinguishable (a.)
definition: Inextinguishable.

Unextinguishable is a 16 letter word that begins with a U and ends in an E

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