I have not heard that term used in that context. Usually a "secondary" refers to a secondary public offering where a public company goes back to the markets and sells more shares to raise more cash.
In VC investing, there is often a "follow-on round" where the company raises additional money from existing VCs after achieving certain objectives (or due to unforeseen delays in the business plan). Usually a follow-on round is not explicitly planned out. It might be anticipated that this round will get the company to X date then you'll need to raise more money, but usually the terms of the follow-on are not committed in advance.
If the terms of multiple investment events are agreed in advanced, that is usually considered a "tranched" investment. For example: we'll give you $X now and if you get the prototype working we'll give you $Y more, then when you sell the first N customers we'll give you another $Z to scale it. This is usually not preferred by the founders or executives.
Any time you hear a term that seems unclear or ambiguous, don't be afraid to ask them what they mean. It's better to clarify immediately than to leave a miscommunication hanging around for weeks.