Senescent means that a person or thing is no longer growing or developing. This might be because the person or thing is no longer young, or it might be because the environment is no longer suitable for growth.
Telomeres are pieces of DNA that protect chromosomes from becoming damaged. As we age, our telomeres get shorter, which means that our chromosomes are at risk of becoming damaged.
When something is bunched up, it is tightly bound together. This can be a good or a bad thing.
To be rejuvenated is to feel like you are feeling better than you have in a long time. You might be rejuvenated because you have recovered from an illness, or you might be feeling rejuvenated because you are starting a new phase in your life.
To be reinvigorated is to be brought back to life, to be made new again. When a company is reinvigorated, it is usually because it has a new leader who is able to bring new ideas and energy to the organization.
Secreting means releasing something into the environment. When you secrete a hormone, you are releasing it into the environment to control or influence the behavior of other people.
Weirdly is used to describe something that is very unusual or unexpected. When you say that something is weirdly shaped, you mean that it is not the usual shape for that kind of object.