Everybody is spiritual, this what one of my teachers said once when I asked her, “Is that person spiritual?” The level of our spirituality may differ. A nice definition of the spiritual person from the same teacher: He/she is a person who wakes up every day wanting to be better than the previous day!
Before coming to the definition of the spirituality (from my point of view) let me be clear about the fact that spirituality has nothing to do with a particular belief or action that you need to adopt. It depends on understanding and being connected to yourself and the universe. If you ask one thousand spiritual people about what spirituality means to them, they may give you one thousand different answers, all of them are correct.
So, what I am suggesting below are my definitions of spirituality according to the way that I understand it, and according to the level that people are in. I came up with this from my journey growing up spiritually and teaching and helping others in their journey. I will leave it to you to adopt the definition that best resonates with you.
Perhaps the first and simplest level is to understand that you are a lovable creature of God and that we are on earth to enjoy our stay and learn from that journey. We are here not to suffer. Even though some suffering is inevitable, it happens to teach us and make us stronger. We are allowed to have fun as much as we can, the only restriction is not to cause harm to anyone.
I will leave the characterization of (not to cause harm) to you, and to your standard that you should set to yourself. Why I say that is because if I start discussing this topic, I will end up writing hundreds of pages. Just take for example smoking or drinking alcohol. By some people's standards, they cause harm and we should avoid them. For others they are not, especially if they are taken on a moderate level.
The next level of spirituality is when you understand the universal laws and apply them to your life; especially the Law of Attraction. You start co-creating your own reality. You know that raising your vibration, being happy and having fun is a must on earth.
Another level of spirituality is to recognize that you are a spirit having human body experience, and you are surrounded by beings to help you with this experience. To realise that you are part of the One and that connection with the source is something you are eager for.
Maybe one the biggest levels of spirituality is when you become a fully enlightened person, and you start helping others in their journey.
All these levels are not rocket science, they can overlap and change. In short it is my current understanding of spirituality and that it is not a right definition that applies to all.