The phrase "what's going down" is an informal way to ask about current events or activities. Several synonyms for this phrase include, "what's happening," "what's going on," "what's new," and "what's the latest." Other similar phrases include "what's popping," "what's shaking," "what's cracking," and "what's cooking." These phrases are often used in casual conversation or when catching up with friends. While they are informal, they can be a great way to break the ice and start a conversation. It is important to note that these phrases are not appropriate for professional settings or formal conversations.