Final answer:
The word 'piquant' refers to something that is pleasantly sharp in taste or interestingly provocative, making 'attractive' the most fitting answer from the options.
Step-by-step explanation:
The word 'piquant' is an adjective that describes something that has a pleasantly sharp taste or appetizing flavor. It can also refer to something that is interestingly provocative or stimulating, often in a sexual or intellectual manner.
Therefore, among the provided options, meaning 3) attractive is the closest in definition, particularly when considering something appealing or stimulating in taste or appeal. The word is quite distinct from the other options, as 'spurious' means false or fake, 'immutable' means unchangeable or unalterable, and 'synonymous' means having the same or nearly the same meaning as another word.