beetle (v): “probably used by Shakespeare with some reference to eyebrows;” to hang/ project threateningly, whose etymology originates from beetle (adj), which describes something as projecting from a brow or ridge of a mountain. According to the (adj) definition, Shakespeare derived one of the (v) definitions.
secondary (v) definitions: to beat something with a beetle to flatten/crush it; “to emboss fabrics by pressure from figured rollers;” to go/fly off (like a beetle).
Horatio What if it tempt you toward the flood, my lord,
Or to the dreadful summit of the cliff
That beetles o’er his base into the sea,
And there assume some other horrible form,
Which might deprive your sovereignty of reason
And draw you into madness? think of it:
The very place puts toys of desperation,
Without more motive, into every brain
That looks so many fathoms to the sea
And hears it roar beneath. (Act 1 Scene 4, Lines 70-79)
In this passage, Horatio warns Hamlet about following the Ghost because it might lead Hamlet astray and make him go mad. The definition to hang/project threateningly is being used in this passage; the cliff is not just a piece of land projecting out into the sea, but it is projecting in a manner that is threatening. Horatio describes the cliff as a place that corrupts the mind of whomever visits there, making them hopelessly desperate. This evokes an image of people committing suicide when they are truly desperate of their condition on earth, which is a common theme in a lot of Shakespeare’s tragedies. In this case, Horatio is trying to prevent Hamlet from possibly being misled by the Ghost to the cliff, where he can jump off and drown himself in the sea. This partially foreshadows the death of Ophelia in Act 4 Scene 7, where she drowns herself in the stream because of the death of her father: Polonius. She became desperate and mad, which is evident by all the singing she does throughout Act 4 Scene 5, so she drowns herself. Beetle does not have much significance to the poem as a whole, but it offers context to a passage that has a significance to the overall poem. The word helps with the imagery of the poem to illustrate one of the common themes of Shakespearean tragedies: suicide as a result of helplessness and desperation.