Muqatil bin Hayyan said: "Tabarruj is when a woman puts a Khimar on her head but not fastening it properly so her necklaces, earrings and neck, and all of that can be seen. As a result of this, these are all exposed from her. This is Tabarruj" (Mukhtasar Tafseer Ibn katheer, volume 3, page 94)
Imam Al-Qurtubee (rahimahullaah) said: "From the ways of Tabarruj is that a woman wears two transparent garments that describe her body" (Tafseer Al-Qurtubee, volume 12, page 310)
Imam Abdur-Rahmaan Ibn Naasir As-Saiadee (rahimahullaah) said: This (ayah) means: Do not go out whilst you are beautified or perfumed, as the women of the Days of Ignorance used to do since they did not have any knowledge or religious characteristics. (Tafseer Ibn Sa'adee, volume 6, no.107)
Imam Al-Albanee (rahimahullaah) said: "Tabarruj is when a woman exposes her adornment, body features and all that she is obligated to cover which invites the desires of men" (Mar'at-il-Muslimah, page 54)
The Messenger of Allaah (may the peace and blessings of Allaah be upon him) said: "And the worst of your women are the ones who commit Tabarruj, who strut around in arrogance. They are the hypocrites. None from among them (i.e. these women) will enter Paradise except (those who are) like the rare crow." (Reported by al-Bayhaqi in his Sunan 7/82) and authenticated by al-Albanee in his as-Saheehah (4/1849)