What is synthetic biology?

Synthetic biology is a research area that integrates multiple methodologies from various disciplines to create new biological parts or to redesign existing biological systems, then finally to create new life forms.
Such as
Squeezing entire 16 yeast chromosome into one (Shao et al., 2018; Luo et al.,2018)
Redesigning the plant photorespiratory pathways to increase plant size (South et al., 2019)

Reference:
Shao, Y., Lu, N., Wu, Z. et al. Creating a functional single-chromosome yeast. Nature 560, 331–335 (2018). https://doi.org/10.1038/s41586-018-0382-x
Luo, J., Sun, X., Cormack, B.P. et al. Karyotype engineering by chromosome fusion leads to reproductive isolation in yeast. Nature 560, 392–396 (2018). https://doi.org/10.1038/s41586-018-0374-x
South P.F., Cavanagh A.P., Liu H.W., Ort D.R.  Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field. Science 363 (6422):eaat9077 (2019). doi:10.1126/science.aat9077