This article discusses the meanings of mathematics teaching forged in the reflections promoted in a lesson study. Guided by the question "What meanings of teaching in mathematics are constructed from reflections promoted in a lesson study?" and based on Isabel Alarcão's (2018) concept of teaching, we examined four editions of a lesson study, two with teachers of the early years of elementary school, one with mathematics teachers from the final years of elementary school, and one with high school mathematics teachers. Each lesson study cycle was organized in twelve two-hour meetings and involved an average of eight teachers per cycle. The participants are teachers from the state public education system in Rio Grande do Sul, Brazil. The empirical material consists of the researcher's field notes, the participants' logbooks, transcripts of the sessions, and interviews conducted at the end of the cycles. Qualitative and interpretative analysis showed that the reflections promoted in the lesson study revealed that mathematics teaching involves various meanings including educational action, social commitment, and pedagogical transformation.