What do the following things mean?
1. Big nose (in figurative sense)
2. Big foot (in figurative sense)
3. screwball comedy
4. high five (except for its use in the game)
The first two I have not heard as idioms (unless you mean 'nosy' - a person who takes too much interest in another person's business).

Screwball comedy is one that relies a lot on physical humour and slapstick, also 'vulgar' comedy (i.e. jokes about farting).

A high five is where two people hold their hands high and slap them together.
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You're right, 'big nose' and 'big foot' are not idioms. I haven't heard of 'screwball comedy' and I wasn't sure that a 'high five' was one or not (idiom, that is).
But surely there are more important features of idiom people are always forgettinga bout, like you can't say 'more or fewer' or 'more or little', it must be 'more or less'. These are the kinds of things people nowadays need to know about, additionally with words like 'fewer', which nobody seems to be able to use at all! In fact, I think I am going to go and start a thread on my indignation of the misuse of the word 'less'.

So long, so short,

Is 'high five' synonymous with 'give sb a five'?
I heard the first two from tv. So possibly they are idioms (may be not used that much or have become obsolete).