readily flammable wood used as tinder, especially when made soft by fungi. Knocking on wood, also touch wood, is an apotropaic tradition of literally touching, tapping, or knocking on wood, or merely stating that one is doing or intending to do so, in order to avoid "tempting. Touchwood definition, wood converted into an easily ignitible substance by the action of certain fungi, and used as tinder; punk. 6 days ago · UK informal (US knock on wood) said in order to avoid bad luck, either when you mention good luck that you have had in the past or when you mention hopes you have for the future: The deal will be agreed on Wednesday, touch wood. Touch wood is an example of a superstition: something that we do in order to have good luck. Video shows what touch wood means.