1) Outside, the fog was thick and impenetrable.

2) They found the jungle virtually impenetrable.

3) I find his style somewhat impenetrable.

4) The fortifications of the castle were massive and impenetrable.

5) The trees formed a dark and impenetrable barrier .

6) Either side of the river is dense, impenetrable jungle.

7) Their jargon is impenetrable to an outsider.

8) This history book is completely impenetrable to me.

9) Her expression was impenetrable.

10) The language of this document would be impenetrable to anyone except a specialist.

11) Valerie's views on Gerald were impenetrable.

12) Their bushes form an impenetrable hedge.

13) His books are notoriously impenetrable.

14) An impenetrable fog halted traffic.

15) Just a short time ago the forest was impenetrable ... and safe.

16) We were cast into impenetrable blackness,(http://sentencedict.com/impenetrable.html) with the rain still cascading down and that devilish thing on the loose!

17) They stared silently at the impenetrable curtain surrounding the ship, and each face was tense with anxiety.

18) Feminist organizations and the media appeared almost impenetrable to us.

19) But this normally impenetrable barrier is easily breached by fat-soluble ethanol molecules, which slip through like little ghosts.

20) The Japanese market used to be more or less impenetrable.

21) Some of the lyrics on their latest album are completely impenetrable.

22) But they come to realise that they are imprisoned by a transparent but impenetrable wall, which can never be crossed.

23) It's my fault because my notes were so damn impenetrable!

24) For the past half-hour she had been feeling distinctly uneasy as the ever-present shadows had deepened into almost impenetrable blackness.

25) The fire filled the room with a tawny, saffron light and poured pools of impenetrable shadow in the far corners.

26) We followed their tracks down into the swamp where a recent clearcut had left impenetrable thickets of young fir.

27) I accepted to review this book because for me integration has always been a somewhat impenetrable part of quantitative chromatographic analysis.

28) That was until Norman Tebbit spotted what he believed was the biggest chance of holing the impenetrable protective layer around the bill.

29) The gnarled tree trunks-white mulberry and rich brown acacia-formed a perilous and nearly impenetrable net.

30) Work-inhibited children have erected emotional barriers to education and, in response to demands by adults, these barriers become more impenetrable.