You should have instructions for the meter - but I would guess that means High - above the range the meter can cope with.
Drinking lots of water and then washing hands and retesting would be my first thought
Yes, it means your reading is high and off the scale. As @Resurgam says, drink water, then drink some more. Don't eat anything with carbs in it, and test again in half an hour.
Simply means your meter has detected a very high BG.
How high depends on your meter. The user manual (which is likely to be online if you have lost it) will tell you how high ... or at least the minimum BG (usually "HI means the BG is higher than ...)