"Funsies" is an informal term used to describe engaging in an activity purely for fun or enjoyment. While this word might not have many synonymous alternatives, there are some alternatives that embody the essence of lighthearted amusement. Words like "playfully", "merriment", "levity" or "joviality" can be used to convey a similar sense of enjoyment. Additionally, one could use expressions such as "for kicks", "for a laugh" or "to have a good time" to replace the term. However, it is important to note that "funsies" is a colloquial and casual word that may not always have precise synonyms, especially when capturing its specific connotation of carefree and enjoyable endeavors.