The Collaborative International Dictionary of English v.0.48:

Thick \Thick\, n.
   1. The thickest part, or the time when anything is thickest.
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            In the thick of the dust and smoke.   --Knolles.
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   2. A thicket; as, gloomy thicks. [Obs.] --Drayton.
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            Through the thick they heard one rudely rush.
                                                  --Spenser.
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            He through a little window cast his sight
            Through thick of bars, that gave a scanty light.
                                                  --Dryden.
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   Thick-and-thin block (Naut.), a fiddle block. See under
      Fiddle.

   Through thick and thin, through all obstacles and
      difficulties, both great and small.
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            Through thick and thin she followed him. --Hudibras.
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            He became the panegyrist, through thick and thin, of
            a military frenzy.                    --Coleridge.
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