Menyelesaikan persoalan matematika memerlukan proses berpikir, baik dalam menganalisis soal hingga menemukan konsep dari penyelesaian masalah tersebut. Salah satu meteri yang tergolong sulit yaitu materi geometri, hal ini karena penyelesaian masalah geometri tidak hanya membutuhkan hafalan rumus melainkan membutuhkan pemahaman konsep. Kemampuan berpikir reflektif dibutuhkan dalam matematika sebagai wadah untuk mengembangkan kemampuan peserta didik dengan menggunakan konsep yang telah dipelajari sebelumnya untuk mengatasi berbagai kebingungan dalam menyelesaikan masalah matematika. Materi Penelitian ini bertujuan untuk memaparkan karakteristik berpikir reflektif mahasiswa PGSD Universitas Borneo Tarakan dalam menyelesaikan masalah geometri. Jenis penelitian ini adalah penelitian kualitatif deskriptif. Pengumpulan data terdiri atas lembar tes, transkip think-aloud, dan wawancara mendalam. Triangulasi data yang digunakan yaitu triangulasi metode. Hasil penelitian menunjukkan mahasiswa memenuhi indikator aspek berpikir reflektif pada aspek techniques, monitoring, insight, dan conceptualization pada saat menyelesaikan masalah geometri. Terdapat empat karakteristik berpikir reflektif mahasiswa dalam menyelesaikan masalah geometri (1) mengalami kebingungan, kemudian ditindaklanjuti, dan menemukan solusi. (2) mengalami kebingungan, kemudian ditindaklanjuti, lalu mengalami kondisi kebingungan lagi, kemudian ditindaklanjuti, kemudian mengalami kebingungan lagi, lalu ditindaklanjuti kembali, dan menemukan solusi. (3) subjek mengalami kebingungan, kemudian ditindaklanjuti, lalu menyadari kesalahan, lalu ditindaklanjuti kembali, kemudian menemukan solusi. (4) subjek mengalami kebingungan, lalu ditindaklanjuti, kemudian menyadari kesalahan, lalu ditindaklanjuti kembali, lalu menyadari kesalahan lagi, kemudian ditindaklanjuti kembali yang akhirnya menemukan solusi.

Kata Kunci: Berpikir Reflektif, Karakteristik, Masalah Geometri

Solving mathematical problems requires a thinking process, both in analyzing the problem and finding the concept of solving the problem. One of the materials that were classified as difficult material is geometry. It is because solving geometry problems does not only require memorizing formulas but requires understanding the concepts. The ability to reflectively is needed in mathematics as a forum to develop the abilities of students by using concepts that had been studied previously to overcome various confusions in solving mathematical problems. This research material aimed to explain the reflective thinking characteristics of PGSD students of Tarakan Borneo University in solving the geometry problems. This type of research was descriptive qualitative research. Data collection consisted of test sheets, think-aloud transcripts, and in-depth interviews. The data triangulation used method triangulation. The results showed that students met the indicators of reflective thinking aspects in the aspects of techniques, monitoring. insight, and conceptualization when solving the geometric problems. There were four characteristics of reflective thinking of students in solving geometry problems, they were (1) Experiencing confusion, then being followed up, and finding solutions. (2) Experience confusion, then follow up, experience a state of confusion again, follow up, experience confusion again, follow up again, and find a solution. (3) The subject experienced confusion, then was followed up, realized the error, acted back up, found a solution. (4) The subject experienced confusion, then followed up, realized the error, acted back up, realized the mistake again, followed up again who finally found a solution. Keywords: Reflective Thinking, Characteristics, Geometry Problems