The American Heritage Dictionary lists bollard as 'Chiefly British', and indeed this is a word that I hadn't encountered before I lived here, though I'd certainly encountered the things before.
A bollard (in its most frequent sense in BrE) is a post that is used to get in the way of traffic--for instance to keep cars from driving or parking on the (BrE) pavement/(AmE) sidewalk (like the ones on the left) or to direct cars toward(s) the correct lane (see right). There's a scene I like in the film The Nine Lives of Tomas Katz that involves some paranoid bollards. But then again, I like every scene in that film. It's not a film that would be to everyone's taste (I saw it in a Paris cinema's season of 'British eccentrics'), but it's one of those films in which the city (London) is at least as much of a character as those that are played by actors.
Prior to my residence in Britain, I would have called bollards posts. Oh, what an impoverished vocabulary I had back then! But then one does come across more bollards in the UK than in the US. Sometimes they're there for no obvious reason. For example, on a two-way road near my house, there is a bollard that makes traffic going down hill give way (AmE yield) to traffic that's coming up the hill. Since the road is wide enough at this point to let the traffic go both ways, the bollard is just there to slow down the cars that are going down the hill. I can't see why they didn't choose another way to slow the traffic that wouldn't involve the creation of traffic (BrE & regional AmE) queues (general AmE lines). For instance, one could use a (BrE [originally] & regional AmE) sleeping policeman (other AmE speed bump; BrE & AmE speed hump; BrE road hump). Better Half has just called this bollardy arrangement a chicane, another word that only entered my (passive) lexicon after I moved here. The term comes from motor racing, where it usually refers to a little kink in the racetrack, but it's extended here to include the type of traffic slowing measure described above, and like the one (that's barely visible) in this picture from Lancashire.
Sometimes the word bollard is used (in BrE) to refer to the thing on the left, though such things are usually termed traffic cones in BrE and pylons in (at least my dialect of) AmE. Pylon, of course, can also refer to the electrical type of thing to the right--in either dialect. A strange piece of lexicographical trivia is that American Heritage doesn't record the 'traffic cone' sense of pylon, while the OED does (and marks it 'U.S.').
In other news, I was away playing Scrabble again this weekend (hence the lack of blogging), and, as often happens in such situations, I was twice mistaken for Canadian. That brings the Canadian count to five instances in five months. (I also got one instance of "I usually don't like American accents but...".)
Perhaps it's a good thing that I didn't have a chance to blog, as I believe the blog is starting to work against me. I mocked mushy peas, and, lo and behold, five days later my application for UK citizenship was turned down. They say it's because some of my paperwork didn't arrive on time, but I think we can read between the peas...