basilisk (noun)

1 : a legendary reptile with fatal breath and glance

basilisk (adjective)
: suggesting a basilisk : baleful, spellbinding<the eyes … with all their blaze of basilisk horror — Bram Stoker>

[M-W's Col. Dic]

"baleful" and "spellbinding" aren't nearly synonymous in meaning - "baleful" suggests harmfulness but, I suppose, "spellbinding" is free from any such suggestions.

Then, how come the dictionary has listed them side by side? Please guide me.
A basilisk possesses either and both qualities.
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Thank you, Mr Micawber.
A basilisk possesses either and both qualities.

I'm confused by your use of "either and both". Should I interpret it as a basilisk could either be baleful or spellbinding, or both? Please guide me.

The adjective applied could refer to either or both qualities.