There are several synonyms for the word "declaiming" that can be used to convey the act of speaking in a forceful, theatrical manner. Some of these synonyms include "orating," "pronouncing," "announcing," "uttering," and "speaking grandiloquently." Other words that may be used to describe the same action include "exclaiming," "proclaiming," "declaring," and "asserting." While each of these words may carry slightly different connotations, they all share a similar sense of speaking with authority and conviction, often for the purpose of making a persuasive or passionate argument or statement.