Would an alien chestburster be classified as a parasite or as a hybrid?

Question

Aliens or Xenomorphs, form the Alien franchise go through several stages of development.

One of these is hard to define. The chest burster feeds on its host like a parasite,

Wiki - Parasitism

Parasitism is a type of non mutual relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host.

But its shape and form is determined by the host, like a hybrid.

Wiki - Hybrids

In general usage, hybrid is synonymous with heterozygous: any offspring resulting from the mating of two distinctly homozygous individuals

Which of these descriptions is most accurate? Can both be applied to the same creature? If not, then what sort of creature is a chestburster?

Answer 1

TL;DR: "Yes, both"

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The question as written seems to imply - intentionally or not - that there is some sort of contradiction between the terms. But in biology, the two terms are fully orthogonal and not contradictory at all.

Parasitism is a type of non mutual relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host.

Based on that definition, chestburster is unquestionably a parasite. It feeds off of its host's body.

Hybrid has several possible definitions in biology, but in this case it probably is meant to be a taxonomic hybrid:

... offspring resulting from the interbreeding between two animals or plants of different species. (src: Keeton, William T. 1980. Biological science. New York: Norton. ISBN 0-393-95021-2 page A9.)

While technically speaking, Xenomorphs are not part of sexual breeding process between the Queen and the host, the hybridization DOES occur via "Horisontal gene transfer" as per Xenomorph wikia.

Due to horizontal gene transfer during the gestation period, the Alien also takes on some of the basic physical attributes of the host from which it was born, allowing the individual Alien to adapt to the host's environment.

Therefore, you can validly call chestburster a hybrid depending on how narrow a definition of the term you pick, though a biologist might quibble with you (but most likely, they will agree)