In practice
A spinning top shows a period of real two-way trading that ended close to where it began. Traders read it as a market catching its breath: neither buyers nor sellers were willing to commit.
After a long run, several of them in a row suggest momentum is fading. In the middle of a range they simply confirm that nothing is happening.
What to watch for
On its own it is one of the weakest signals on a chart. Treat it as a description of indecision, and wait for the market to show which way it resolves.