Undertaking. Enterprise, engagement, attempt, adventure, business, effort, endeavor; experiment, venture, interest, affair, matter, concern.
Ant. Leisure, inactivity; recreation.
Undulation. Waving motion; vibration; wavy outline; pulsation; oscillation, swelling; wave, ripple.
Ant. Equilibrium; arrestation, standing; plain, tableland.
Uniform. Unchanging, equable, consistent, homogeneous; consonant; regular, constant, invariable, steady; similar, unvaried, alike.
Ant. Heterogeneous, variable, varying, diverse; irregular, inconsistent, erratic, eccentric, unsymmetrical.
Union. Unity, connection, concord, combination, confederacy, alliance; coalition, conjunction; harmony, concert, agreement; league, confederation, consolidation; oneness, juncture, unification.
Ant. Disconnection, separation, disjunction, disunion, divorce, severance, analysis, dissociation, contrariety, decomposition, division, schism, partition, discord, disagreement, secession, disruption; multiplication, diversification.
Unique. Sole, only, unmatched, unequalled, unparalleled, singular, peculiar, exceptional, rare.
Ant. Common, universal, everyday, commonplace, ordinary, familiar, vulgar, mean.