To skylark means to play around or to act silly, especially when you should be serious.
Skylarking is usually seen as fun, but it can also be seen as not responsible.
Examples:
The kids skylarked in the yard instead of doing their homework.
Stop skylarking and pay attention!
She skylarked during the meeting and made everyone laugh.
The dog skylarked around the park, chasing its tail.
The monkeys skylarked all day long, swinging from tree to tree.
We skylarked in the sun all afternoon, forgetting about our work.