What is the meaning of....

means 意思為「方法」，by all means 即「以任何方法」，意思係肯定會做。如風水佬可能會講：
Avoid getting near water by all means! 你忌水，一定要催避！
樓上其中一個答案，講到用o黎答人，如：
A: Can you hold this for me? B: By all means.
其實等於 certainly（當然可以）。

當然可以；務必
例："May I borrow this book?" (我能借這本書嗎？)
"By all means." (當然可以。)

its mean like overall