This is the 5448th most frequent Spanish word.
ocasional
Occasional; happening or appearing infrequently or irregularly.
In this sentence, 'ocasional' is used as an adjective describing the frequency of reading novels, implying that the action is not regular but happens sporadically.
Yo soy un lector ocasional de novelas históricas.
I am an occasional reader of historical novels.
Here, 'ocasional' is an adjective indicating the periodic and irregular occurrence of celebrity visits to the restaurant.
El restaurante tiene visitas ocasionales por parte de celebridades.
The restaurant has occasional visits from celebrities.
'Ocasionales' in this context modifies 'reuniones' suggesting that the meetings are not regular but happen from time to time.