Meaning of Japanese Kanji

There are 5 foreigners in our office now.
The common language of our company is English.
But, we use Japanese when we send mail to Japanese and we speak with Japanese.
I am sometimes questioned by foreigner's colleague about meaning of Japansese kanji.
I was the science course..... I do not know a lot of Kanji.
In my new electronic dictionary is including a Japanese dictionary!!!!!
It is very useful for me in our office.
Can you explain the meaning of Japanese kanji below?

・流石(Sasuga)・・・This kanji is not read as "Nagareishi" .
・五月雨式(Samidare-shiki)・・・This kanji is not read as "gogatsuame-shiki".
・御足労(Gosokurou)・・・This kanji is not read as "Oashirou" .