Translation:I played a lot yesterday.
Well; Jim Breen's dictionary (the one used by the Aedict app as well) says that 遊ぶ means "to play; to enjoy oneself; to have a good time", so I guess that includes "having fun", right? "Hang out" seems like a good translation for most cases (thanks for that one!), but I feel that in this case the sentence implies that "I enjoyed myself very much", given that たくさん (at least "I hang out a lot yesterday" doesn't make so much sense to me). And "having a lot of fun" is the only expression I found that doesn't sound very unnatural. I had to search that one up, because some Japanese friend invited me to 「あそびます」with her and a friend some time ago, and the instant translator's "play" sounded kinda suspicious (xD). I also asked someone and I think what I was told also involved having fun in some way, but I don't remember so much anymore...
I guess we would need someone native here to clarify.
Why isn't it possible to report a sentence because my answer should be accepted on "type what you hear" exercises. WHY? 昨日 should be accepted instead of きのう, but it's not, and I don't have the possibility to tell the creators of this course about it! It's extremely infuriating.
How broad is the word asobu? In English the word 'play has a number of uses intransitive and transitive ( I played soccer, the guitar etc...). From my research, asobu seems limited to intransitive forms of enjoyment. So:
I played outside
私は外で あそびました watashi wa soto de asobi mashita
I played with my friends outside
私は友達と外で あそびました watashi wa tomodachi to soto de asobi mashita
But for transitive sentences, it seems the 'suru' verb is used instead
I played soccer with my friends
私は友達とサッカーをしました Watashi wa tomodachi to sakkā o shimashita