This is the 9900th most frequent Spanish word.
bolas
"Bolas" means "balls" in English.
In this sentence, 'bolas' refers to 'balls', specifically snowballs, serving as a descriptor for an object.
Las bolas de nieve son muy divertidas para lanzar en invierno.
Snowballs are very fun to throw in winter.
Here, 'bolas' is part of the colloquial expression 'echar bolas', implying wasting time or not being serious.
Él siempre está echando bolas en lugar de estudiar.
He is always goofing around instead of studying.
In this case, 'bolas' refers to spherical ornaments (Christmas balls) decorating the tree.