Help! thanks!

[mffpc]

I was trying to look up this word in the dictionary but I didn't found anything so could you please tell what does all-time means? Well, I have the main idea of the word but I want a dictionary explanation.
This is the whole sentense: "Youth activism levels are at all-time high."

Thanks

[Raymott]

I was trying to look up in the dictionary for "all-time" but I didn't find anything, so could you please tell me what does it mean? well, i have the main idea of the word but I want a dictionary explanation.
Context: Youth activism levels are at all-time high.

Thanks

It means "unprecedented". Youth activism levels are the highest in all time, ever. Often it is used for "a long-time high", or when the real "high" is forgotten or never measured.

[hanky]

I was trying to look up this word in the dictionary but I didn't found anything so could you please tell what does all-time means? Well, I have the main idea of the word but I want a dictionary explanation.
This is the whole sentense: "Youth activism levels are at all-time high."

Thanks

Here you are

http://dictionary.reference.com/browse/alltime
http://dictionary.reference.com/browse/all-time