Oct 25 (Reuters) - Pinterest Inc PINS.N posted its slowest quarterly revenue growth in nearly two years and turned a loss, the latest social media platform to fall victim to a slowdown in advertising spending by companies worried about a gloomy economic outlook. Decades-high inflation is forcing companies to make cuts to their marketing budgets this year, driving online player such as Alphabet Inc GOOGL.O, Meta Platforms Inc META.O and Snap Inc SNAP.O to intensely compete for shrinking ad dollars. Pinterest's third-quarter revenue grew 8% to $684.6 million, mirroring a slowdown seen at its bigger rivals.