# new wine

"grape juice." This refers to wine that has not yet fermented.

# wineskins

These were bags made out of animal skins. Alternate translation: "wine bags" or "bags made of skin"

# the new wine will burst the skins

When the new wine would ferment and expand, it would break the old skins because they could no longer stretch out. 

# the wine will be spilled

"the wine will spill out of the bags"