This is the 413th most frequent Catalan word.
santa
The Catalan word "santa" means "saint" (feminine) or "holy" (feminine).
In this religious context, 'santa' is used as an adjective meaning 'holy' or 'sacred' to describe a night.
La nit de Nadal és una nit santa.
Christmas Eve is a holy night.
Here, 'Santa' is part of a proper noun, referring to a saint in honorific usage.
La Santa Teresa va ser una gran escriptora.
Saint Teresa was a great writer.
In this case, 'santa' metaphorically describes someone exceedingly kind or virtuous.