'Pleach' is not a common word, and its use in modern English doesn't seem to include arms at all, only things like tree branches and hair. I would suggest deleting this entry or changing the English side to 'cross one's arms.'
I'm not typing out all the OED entries here because I know you have it at hand, but the only example I saw that refers to arms is a single line from Shakespeare, Antony and Cleopatra, 1606. It appears to be only a one-time poetic image, that is, a metaphor that readers ought to be able to understand if they simply know that 'pleach' means intertwine or interlace. Tellingly, my web search turned up absolutely zero other examples, just that one line from that one play:http://www.google.com/search?hl=en&q=
So apparently it wasn't a fixed phrase even back then, or else it would probably have shown up, since there are lots of Renaissance texts on the web.
I might also suggest double-checking the other entries in the area of crossing/folding arms/legs. If they refer to people, they should all say 'one's' instead of 'the,' since THE legs or THE arms implies an inanimate object such as a chair or table.
Also, although the verb 'cross' is IMO more common in this context than 'fold,' at least in AE, I don't seem to find the most normal one, 'cross one's arms,' at all.
And it might also be nice to add 'fold one's hands = die Hände falten' and 'fold (its) wings = die Flügel anlegen.'
BTW the arrow links for expanding Optionen and Legende on the dictionary page don't seem to be working at the moment -- don't know if it's just me or what.