Boastful about himself, his personality, his significance and in speech!
Allaah (The Most High) said in Soorah Luqmaan Ayah: 18
وَلَا تُصَعِّرْ خَدَّكَ لِلنَّاسِ وَلَا تَمْشِ فِي الْأَرْضِ مَرَحًا إِنَّ اللَّهَ لَا يُحِبُّ كُلَّ مُخْتَالٍ فَخُورٍ
[وَلَا تُصَعِّرْ خَدَّكَ لِلنَّاسِ –And turn not your face away from men with pride]; Imaam as-Sa’di (rahimahullaah): Do not turn away and frowning at the people with your face, being arrogant towards them and exalting (yourself).
[ وَلَا تَمْشِ فِي الْأَرْضِ مَرَحًا ۖ –Nor walk in insolence through the earth]; That is: out of vanity, boasting about blessings, forgetful of the one who bestowed it upon you (i.e. Allaah) and being amazed with yourself.
[إِنَّ اللَّهَ لَا يُحِبُّ كُلَّ مُخْتَالٍ فَخُورٍ- Verily, Allah likes not each arrogant boaster]; boastful about himself, his personality and significance, and in his speech.
[Source: Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam Al-Mannaan]