Updated: Jan 12, 2020
The meaning of this expression depends on the context in which it is used, however, the most common meanings for this word would be: strive, persevere, not give up, give the best of yourself, overcome, ..., in front of a difficulty.
However, in Japan the expression goes beyond its simple literal meaning, becoming a way of understanding life, called the culture of effort. It is the commitment that when you start a thing you do not give up until you finish it, a sincere commitment of effort before the difficulties of life.
In Japan you always have to give the best of yourself and make the most effort in any situation, it is what is expected of you and it is not something to be proud of or to brag about, it is normal. The more you try, the more admirable you will be.
You try your best for yourself, for your family, for your friends, for your company and sometimes even for society.
The social concept of 'ganbaru' can be quickly understood when we think of Japan desolated after World War II and we see how the country passed, in a few decades, from being desolate to being the second world power, now the third after China.
This concept of 'ganbaru' can also be found if we think that it is a country that, although it is hit again and again by numerous natural disasters, overlaps itself again and again in a way that almost seems like a miracle.