adverb

1. (sequence) Used to mark the beginning of the last in a list of items or propositions.

   “Firstly, that's illegal; secondly, it has serious disadvantages; thirdly, it's not necessary; and lastly, did I mention that it's illegal?”

2. (discourse marker) Used to signal that the speaker is about to yield control of the conversation.

Synonyms: all in all, at last, finally, in conclusion, in the end, to conclude, to sum up, ultimately