People smack twice before yawning because when you smack it brings up some of the air you need to yawn.
twice
Many people (not necessarily scientiest or meteorologists) think that lightning will not strike the same place twice. So they say that it is rare for lightning to strick twice, meaning twice at the same place. This term is used to imply something that is rare.
biannually means twice a year
He is interested.
Treat me just as you would anyone without Tourette's Disorder. I am who I am in spite of my tics.
meaning: "not twice for the same".
Double or twice
twice
A repetative Task as in being done twice.
you turn the right side twice
It is used for both senses, but the proper meaning is twice a week.
Bimonthly is a term meaning 'twice per month'.