Old Norse þvert ‘across’, originally neut. of thverr (transverse, across), cognates include Old English  (transverse, perverse, angry, cross), Danish þweorh , Gothic tvær ( 𐌸𐍅𐌰𐌹𐍂𐍃 þwairs, “ angry ”), Dutch (cross-grained, contrary), German dwars , from quer Proto-Germanic , altered by influence of *þwerhaz Proto-Germanic (to turn) from *þweraną Proto-Germanic , from *þerh- Proto-Indo-European (twist). *twork-/*twerk-
thwart ( third-person singular simple present , thwarts present participle , thwarting simple past and past participle ) thwarted
( transitive ) To prevent; to halt; to cause to fail; to foil; to frustrate.
The police thwarted the would-be assassin.
Our plans for a picnic were thwarted by the thunderstorm.
The proposals of the one never
thwarted the inclinations of the other.
: 1918, W. B. Maxwell, chapter 22, The Mirror and the Lamp
Not unnaturally, “Auntie” took this communication in bad part. [… ] Next day she [… ] tried to recover her ward by the hair of the head. Then, thwarted, the wretched creature went to the police for help; she was versed in the law, and had perhaps spared no pains to keep on good terms with the local constabulary.
: 2006, Edwin Black, chapter 2, Internal Combustion 
More than a mere source of Promethean sustenance to thwart the cold and cook one's meat, wood was quite simply mankind's first industrial and manufacturing fuel.
2011 December 10, David Ornstein, “ Arsenal 1-0 Everton”, BBC Sport:
Everton were now firmly on the back foot and it required some sharp work from Johnny Heitinga and Phil Jagielka to thwart Walcott and Thomas Vermaelen.
( obsolete ) To move across or counter to; to cross.
An arrow thwarts the air.
John Milton (1608-1674)
Swift as a shooting star / In autumn
thwarts the night.
Derived terms Edit
to prevent; to halt; to cause failure
thwart ( plural ) thwarts
( nautical ) A brace, perpendicular to the keel, that helps maintain the beam (breadth) of a marine vessel against external water pressure and that may serve to support the rail.
A well made doughout canoe rarely needs a thwart.
( nautical ) A seat across a boat on which a rower may sit.
The fisherman sat on the aft thwart to row.
Related terms Edit
seat attached to both sides of a boat
thwart ( comparative , more thwart superlative ) most thwart
Situated or placed across something else;
Moved contrary with
( figuratively ) Perverse; crossgrained.
(Can we find and add a quotation of Shakespeare to this entry?)
thwart ( not ) comparable
Obliquely; transversely; athwart.
(Can we find and add a quotation of Milton to this entry?)
^ “ thwart” in Douglas Harper, Online Etymology Dictionary (2001).