This is the 11350th most frequent Spanish word.
espontáneos
"Espontáneos" means "spontaneous" or "impromptu."
In this sentence, "espontáneos" is an adjective modifying "eventos," describing events that happen naturally or without external planning.
Los eventos espontáneos suelen ser los más divertidos.
Spontaneous events are usually the most fun.
Here, "espontáneos" describes the characteristic of the friends as acting based on a sudden impulse rather than a plan.
Los amigos fueron espontáneos y decidieron salir de viaje ese mismo día.
The friends were spontaneous and decided to go on a trip the same day.
In this example, "espontáneos" refers to comments that happened naturally without being premeditated.