touchwood

Ususally people would say that when someone said something bad or not something that want to happen in the future, they will touch the wood to prevent it from happening,

like:
i said : i think my boyfriend is cheating on me,
Mr. A: touchwood, dont be silly, it is not going to happen, u dont know that.

something like that,
or

i said : hopefully i will get my money back from this guy on time,
Mr. B: touchwood it is going to happen very soon.

Remarks:

dont use this word in ur homework, or anything that u a going to hand in to others ( in the formal ones ) it is just something people say in a informal way, like causel talking, like talking with a friend, otherwise it is going to make u loss points in the paper....
be careful with that....

Hope it helps

Touch wood ¬ knocking on wood

Knocking on wood, and the spoken expression "knock on wood" or "touch wood" are used as a charm to bring good luck or to avoid "tempting fate" after making some boast or speaking of one's own death.

The expression is usually used in the hope that a good thing will continue to occur after it has been acknowledged. So, for example, one might say: "The rain looks like holding off, touch wood", or "Knock on wood, I'm much better now."

中文意思可解作: 大吉利是, 好彩,...

When one say 'touch wood ', at the same time, one may knock on something wooden nearby with the hand or fingers, or just knock on the head.

Meaning of TOUCH WOOD ( American equivalent KNOCK ON WOOD):
愛爾蘭有一個流傳已久的傳說，認為用手摸木頭可以趨吉避凶。
因此，另一引申含意為「但願繼續保持好運」。
另外一個說法，耶穌被釘在木十字架上，如果碰到這十字架上的話，可以驅除霉運。
To touch wood or knock on wood is a superstition action to ward off any evil consequences or bad luck. It can also be a charm to bring good luck.
There’s also a belief that wood symbolises the timber of the cross.
(Reference: http://www.worldwidewords.org/qa/qa-tou1.htm)

Touchwood 中文意思係"碰碰木頭",
以取吉利,和希望會帶來幸運之動作

外國人常用於當他們在講一些不吉利說話時,例如:我同事被解僱了,
因為他不想也成為下一個被炒的目標,所以通常會立即講"touchwood",
並真的找附近的木頭,或木製品,來觸碰一下,
以希望惡運會遠離佢,而好運自然來也!
這是一個外國人的民間通俗傳統.

touchwood - Anything used as a test or standard (試金石, 標準)
與 Touchstone 同意思.