The term for this type of behaviour is Thread Synchronization. Also sometimes called serialization because the threads must get in line and go through that piece of code serially.
Lock Contention is a dimension that can be used to measure and predict the performance of a piece of code that requires thread synchronization. If 8 threads are contending for a lock vs. 4 threads, that speaks to how slowly your requests are going to complete for instance.
Thread Starvation is what occurs when all threads are busy, but new requests are coming in and there are no threads to service those requests. Thread starvation can be a side effect of contention, but you can have a highly-contentious system blocking everything into single threading without getting thread starvation depending on the size of your thread pool and or the number of work requests coming in.
So in short, when you have multiple threads contending for a single thing, those threads are said to be synchronized - or serialized in some parlances.
Lock Contention on Wikipedia
Starvation on Wikipedia