Terra Firma.  An estate in land.

Tester.  A sixpence:  from Teston, a coin with a head on it.

TETBURY portion.  A **** and a clap.

Thames.  He will not find out a way to set the Thames
  on fire; he will not make any wonderful discoveries, he is
  no conjuror.

Thatch-gallows.  A rogue, or man of bad character.

Thick.  Intimate.  They are as thick as two inkle-weavers.

Thief.  You are a thief and a murderer, you have killed a
  baboon and stole his face; vulgar abuse.

Thief in A candle.  Part of the wick or snuff, which falling
  on the tallow, burns and melts it, and causing it to
  gutter, thus steals it away.

Thief takers.  Fellows who associate with all kinds of
  villains, in order to betray them, when they have committed
  any of those crimes which entitle the persons taking
  them to a handsome reward, called blood money.  It is
  the business of these thief takers to furnish subjects for a
  handsome execution, at the end of every sessions.

Thimble.  A watch.  The swell flashes a rum thimble;
  the gentleman sports a fine watch.

Thingstable.  Mr. Thingstable; Mr. Constable:  a ludicrous
  affectation of delicacy in avoiding the pronunciation
  of the first syllable in the title of that officer, which in
  sound has some similarity to an indecent monosyllable.

Thingumbob.  Mr. Thingumbob; a vulgar address or nomination
  to any person whose name is unknown, the same
  as Mr. What-d’ye-cal’em.  Thingumbobs; testicles.

THIRDING.  A custom practised at the universities, where
  two thirds of the original price is allowed by the upholsterers
  to the students for household goods returned to them
  within the year.

THIRTEENER.  A shilling in Ireland, which there passes for
  thirteen pence.

THOMOND.  Like Lord Thomond’s cocks, all on one side. 
  Lord Thomond’s cock-feeder, an Irishman, being entrusted
  with some cocks which were matched for a considerable
  sum, the night before the battle shut them all together in
  one room, concluding that as they were all on the same
  side, they would not disagree:  the consequence was, they
  were most of them either killed or lamed before the morning.

Thomas.  Man Thomas; a man’s penis.

Thorns.  To be or sit upon thorns; to be uneasy, impatient,
  anxious for an event.

Thornback.  An old maid.

Thorough churchman.  A person who goes in at one door
  of a church, and out at the other, without stopping.

Thorough-good-natured wench.  One who being asked
  to sit down, will lie down.