Humans have rather a lot of meanings, including heavy petting between lovers.
Amongst giraffes, the meaning is no-where near as pleasant. Given the giraffes long thin neck, they cannot charge with their head down, as their neck would likely break. Instead the males stand side by side and swing their long necks at each other and thrust their short horn into the flank of their opponent.
As with other male displays, this can severely injure the males and indeed it is relatively common for the fight to end with one or more too dazed to continue, or in extreme cases knocked out cold.
Certainly, while giraffes can be seen as gentle, their displays show they are not like this all the time and as with any wild animal, needs to be shown a lot of respect, and given plenty of space.