Doff means to remove an item of clothing, but is most commonly meant to take off your hat or tip your hat as a greeting.
Something is off if it is not powered up and available to be used. The computer in the picture is switched off. Off also can be used to indicate something no longer attached to something else: "the branch broke off the tree", or for reducing something: "take ten percent off the price". The opposite of off is on.
A trough is a big, long, shallow bowl that is usually used for giving food or water to animals. Troughs can also be filled with soil and used to grow plants in.
A waffle is a thin cake made from batter in a special device called a waffle iron. Waffle irons usually have a distinctive pattern on them. Waffles are sweet, and are usually eaten for breakfast with melted butter, syrup or jam. Waffle is also the name given to a pattern that looks like a waffle, which is sometimes found on knitted clothing and blankets.