What does 飘然而至 mean?
It means "to breeze (in)".

To examine this in more detail, the phrase 飘然而至 simply means "to arrive" in a 飘然 manner", and 飘然 has a couple of interconnected meanings:


very quickly
unrestrained, unencumbered; carefree
flowing loosely


A good overall translation would be "to breeze (in)". However, the precise translation can be adjusted depending on the context. For example:


这寒冷的冬季飘然而至 -> "The cold winter arrived swiftly."
凤凰涅槃, 飘然而至 -> "A phoenix flies over nimbly."
绝世美少女飘然而至 -> "A peerless beauty breezes in."
飘然而至的感伤 -> "Sentimental sadness sweeps over (me)." (inspired by @TommieC.'s answer)