This is the 14137th most frequent Polish word.
pośmiać
To laugh.
Here, 'pośmiać' is used reflexively with 'się' to mean 'to laugh' or 'have a laugh', emphasizing enjoyment of humor.
Lubimy pośmiać się z dobrych dowcipów.
We like to laugh at good jokes.
In this sentence, 'pośmiać' indicates the result of sharing a laugh due to an amusing event that occurred.
Wczoraj mieliśmy okazję pośmiać się z sytuacji.
Yesterday, we had an opportunity to laugh at a situation.
The use of 'pośmiać się' here suggests the intention to have a laugh together for the sake of making the situation more comfortable.