From Longman Dictionary of Contemporary Englishtouch woodtouch woodBritish English, knock on wood American English said just after you have said that things are going well for you, when you want your good luck to continue → wood
Examples from the Corpus
touch wood• We haven't missed a deadline yet, knock on wood.• I've just been lucky so far, touch wood.• What is more, it might, touch wood, even be in a position to implement some of them.• I've never been in trouble with the police, touch wood.• And I hope I don't - touch wood!• Male speaker Well we are a bit of a lively bunch but I haven't been banned yet ... touch wood! 