1. 
   Plank-Head
   Plank-head is British slang for a stupid person.
   Found op http://www.probertencyclopaedia.com/browse/ZP.HTM
   
   
2. 
   Plank-Head
   Plank-head is British slang for a stupid person.
   Found op http://www.probertencyclopaedia.com/browse/ZP.HTM
   
   
3. 
   plankahead
   1) Warning sign on a pirate ship?
   Found op http://www.mijnwoordenboek.nl/EN/crossword-dictionary/plankahead/1
   
   

Tip: double click on a word to show its meaning.