egg timer
US /ˈeɡ ˌtaɪ.mər/
UK /ˈeɡ ˌtaɪ.mər/

1.
a device for timing the boiling of eggs, typically one that measures a period of three to five minutes
:
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She set the egg timer for three minutes to get a soft-boiled egg.
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The sand egg timer is a classic kitchen tool.