gagging on puree?

El
What does it mean when baby gags on certain puréed food? He loves his homemade baby cereal which is quinoa & formula and he loves sweet potatos. We just tried him on avacado twice. Once last night and he gagged and puked it all up, then we just retried and he started to gag a bit about 3 quarters done so we stopped and hasn't thrown it up.